TEXT  BOOK 

OF 


CYANIDE   PRACTICE 


BY 

H.   W.   MAcFARREN 

f   r 

AUTHOR  OF 

"Practical  Stamp  Mitting  and  Amalgamation." 
"Mining  Law  for  the  Prospector,  Miner  and  Engineer." 


McGKAW-HILL   BOOK   COMPANY 

239  WEST  39TH  STREET,  NEW  YORK 

6  BOUVERIE  STREET,  LONDON,  B.C. 

1912 


COPYRIGHT,  1912 

BY  THE 

McGRAW-HILL  BOOK  COMPANY 


Stanhope 

F.    H.GILSON    COMPANY 
BOSTON,  U.S.A. 


PREFACE 


THE  cyanide  process  is  a  subject  comprehending  many  divi- 
sions, and  one  that  can  best  be  treated  along  some  phase  or  with 
a  special  point  in  view.  The  point  in  view  or  purpose  of  this 
work  is  to  furnish  students,  cyanide  workers,  and  those  generally 
and  technically  interested  in  the  subject,  with  a  practical  and 
technical  exposition  of  the  principles  and  basic  practice  appli- 
cable to  cyanidation  in  general,  and  not  of  the  particular  practice 
at  any  plant  or  locality.  An  exposition  not  too  technical  and 
complicated  or  comprehensive  for  those  who  are  acquiring  or 
about  to  acquire  their  technical  equipment,  nor  too  superficial 
for  the  experienced  operator.  Intended  primarily  to  guide  the 
first  footsteps  and  early  progress  of  those  who  hope  to  eventually 
operate  plants,  the  author  has  used  simple  explanations  and 
many  repetitions  and  references  to  other  parts  of  the  text  in  the 
effort  to  clarify  a  subject  that  is  confusing,  to  say  the  least,  to 
the  beginner.  Desiring  to  produce  a  work  that  will  be  of  use  in 
actual  practice,  rather  than  something  to  simply  add  to  one's 
technical  library,  the  author  has  not  kept  within  academic 
limitations,  but  has  resorted  to  homely  methods  of  explanation 
where  deemed  advisable.  Though  going  into  considerable  de- 
tail, no  branch  of  the  subject  has  been  carried  to  that  point 
where  it  should  be  taken  up  as  a  special  subject.  It  aims  to  lift 
the  careful  reader  and  student  to  that  point  where  he  may  in- 
telligently seek  further  information  in  the  literature  on  investi- 
gations into  special  and  abstruse  details  of  the  subject,  for  which 
purpose  and  as  an  aid  to  the  advanced  worker  an  extended 
Classified  Bibliography  of  the  more  accessible  literature  on  the 
cyanide  process  is  included. 

Where  it  has  been  impossible  to  give  definite  figures  without 
going  into  explanatory  details,  obviously  beyond  the  scope  of 
this  work,  figures  representing  the  average  or  rational  extremes 
in  practice  have  been  given.  The  reader  may  consider  these 
as  carefully  selected  to  represent  accurately  approved  modern 

practice. 

H.  W.  MAcFARREN. 


241260 


CONTENTS 


PAGES 

PREFACE vii 

CHAPTER  I 

HISTORY  AND  DEVELOPMENT 1-6 

Discovery  and  Early  Use  of  Cyanide  —  MacArthur-Forrest  Proc- 
ess —  Development  of  the  Cyanide  Process. 

CHAPTER  II 

NATURE  AND  PROPERTIES  OF  CYANIDE 7-10 

Definition  of  Cyanide  and  Cyanogen  —  Properties  and  Reac- 
tions of  Cyanide  and  Cyanogen  —  Cyanogen  Used  in  the  Cyanide 
Process  —  Difference  between  Sodium  and  Potassium  Cyanide. 

CHAPTER  III 

DISSOLUTION  OF  GOLD  AND  SILVER 11-20 

Reactions  —  Necessity  and  Source  of  Oxygen  —  Bromocyanide 
and  Mercury  Salts  as  Supersolvents  —  Strength  of  Solution 
Required  —  Cyanicides  —  Heating  the  Solution  —  Effect  of  Size 
of  Metal  Particles  —  Effect  of  Crushing  and  Form  in  which  Metal 
is  Held  —  Volume  of  Solution  Required  and  Method  of  Applica- 
tion —  Time  Required  for  Dissolution  —  Silver  Ores. 

CHAPTER  IV 

SUITABILITY  OF  AN  ORE  FOR  CYANIDATION 21-27 

Classification  of  Ores  —  Iron  —  Sulphur  —  Copper  —  Lead  —  Ar- 
senic —  Antimony  —  Tellurium  —  Mercury  and  Cinnabar  —  Zinc 
—  Nickel  and  Cobalt  —  Manganese  —  Carbon  and  Carbonaceous 
Matter  —  Aluminum  and  Magnesium  —  Silver. 

CHAPTER  V 

CHEMISTRY  OF  CYANIDE  SOLUTIONS 28-53 

Classification  of  Cyanide  Tests  —  A.  Free  Cyanide  —  Standard 
Silver  Nitrate  Test  —  Reactions  in  Standard  Silver  Nitrate  Test 
—  Reactions  of  the  Potassium  Iodide  —  Testing  Strength  of  Solid 
Cyanide  —  B.  Hydrocyanic  Acid  and  Acidity  —  Test  for  Hy- 
drocyanic Acid  —  Acidity  Test  for  Hydrocyanic  Acid  —  Nature 
of  Acid  Cyanide  Solutions  —  C.  Total  Cyanide  —  Definition  — 

vii 


viii  CONTENTS 

PAGES 

Test  with  Standard  Silver  Nitrate  and  Alkali  —  Action  of  Double 
Cyanides  —  D.  Protective  Alkalinity  —  Definition  —  Test  for 
Protective  Alkalinity  —  Preparation  of  Indicators  —  Theory  of 
Standard  Acid  and  Alkali  Solutions  —  Preparation  of  Standard 
Decinormal  Acid  and  Alkali  Solutions  —  E.  Total  Alkalinity  — 
F.  Ferrocyanides  and  Ferricyanides  —  Definition  and  Occurrence 

—  Determination  —  G.   Alkaline  Sulphides  and  Sulphocyanides  — 
Definition  and  Occurrence  of  Alkaline  Sulphides  —  Alkaline  Sul- 
phides and  Sulphocyanides  or  Thiocyanates  —  Action  and  Re- 
moval of  Alkaline  Sulphides  —  Application  of  Lead  Acetate  — 
Test  for  Alkaline  Sulphides  —  H.   Available  Cyanide  —  Definition 

-  Test  for  Available  Cyanide  —  I.  Cyanates  and  Total  Cyano- 
gen —  J.  Reducing  Power  —  K.  Assay  of  Metals  in  Cyanide  Solu- 
tion —  Classification  of  Methods  for  Gold  and  Silver  —  Lead 
Tray  Evaporation  —  Evaporation  with  Litharge,  etc.  —  Pre- 
cipitation, Incinerating,  Fusing,  etc.  —  Precipitation  with  Direct 
Cupellation  —  The  Chiddy  Method  —  Assay  of  Base  Metals  in 
Solution. 

CHAPTER  VI 

ALKALINITY  AND  LIME 54-64 

Definition  and  Properties  of  Lime  —  Uses  of  Lime  and  Alka- 
linity in  the  Cyanide  Process  —  Neutralization  of  Metallic  Salts 

—  Lime  and  Alkalinity  in  Zinc  Precipitation  —  Lime  as  a  Neutral- 
izer  of  Carbonic  Acid  —  Dissolving  Effect  of  Al.kalis  upon  Metals 

—  Amount  of  Lime  or  Protective  Alkalinity  Required  —  Methods 
of  Adding   Lime  —  Lime   v.   Caustic  Soda  —  Determination   of 
Causticity  of  Lime,  etc. 

CHAPTER  VII 

ORE  TESTING  AND  PHYSICAL  DETERMINATIONS 65-86 

Facts  to  be  Determined  —  Methods  of  Testing  —  Securing 
Samples  —  Physical  Examination  of  Ores  —  Free  Acidity  —  La- 
tent Acidity  —  Total  Acidity  —  Extraction  Tests  with  Bottles  — 
Percolation  Tests  —  Fineness  of  Ore  Required  —  Sizing  Tests  — 
Amalgamation  Tests  —  Tests  on  Concentrate  —  Summary  of  Small 
Ore  Tests  —  Tests  on  Large  Scale  —  Leaching  Rate  —  Slime 
Settling  Rate  —  Determination  of  the  Cause  of  Low  Extraction  — 
Determination  of  the  Cause  of  Cyanide  Consumption  —  Pre- 
cipitation Tests  —  Specific  Gravity  Determination. 

CHAPTER  VIII 

PERCOLATION 87-107 

Definition  —  Treatment  of  Tailing  Deposits  —  Treatment  of 
Dry  Crushed  Ore  —  Direct  Filling  of  Vats  with  Wet  Pulp  — 
Depth  of  Sand  Charge  —  Arrangement  of  Leaching  Plant  — 
Weak  and  Strong  Solution  and  Their  Separation  —  Application 
of  Solution  to  Treatment  Vats. 


CONTENTS  ix 

CHAPTER  IX  PAGE8 

SLIME  TREATMENT  AND  AGITATION 108-124 

Definition  of  Slime  —  Slime  Settlement  —  Classification  or  Sepa- 
ration of  Sand  and  Slime  —  Pulp  Thickening  —  Charging  for 
Agitation  —  Amount  of  Solution  in  Agitation  —  Strength  of  Solu- 
tion and  Time  Required  in  Agitation  —  Intermittent  and  Con- 
tinuous Agitation  —  Types  of  Agitators. 

CHAPTER  X 

DECANTATION 125-130 

Theory  of  the  Decantation  Process  —  Decantation  Process  in 
Practice  —  Mechanical  Decantation  Processes. 

CHAPTER  XI 

FILTRATION 131-158 

Plate  and  Frame  Filter  Press  —  Filter  Press  Practice  in  Australia 
—  The  Merrill  Press  —  Vacuum  or  Pressure  Leaf  Filters  —  Classi- 
fication of  Leaf  Filters. 

CHAPTER  XII 

PRECIPITATION 159-175 

Reactions  in  Zinc  Precipitation  and  Formation  of  White  Precipi- 
tate —  Clarifying  the  Solution  —  Zinc  Boxes  —  Size  of  Shavings 
—  Weight  of  Shaving  and  Amount  Required  —  Packing  and 
Dressing  the  Boxes  —  General  Care  of  Precipitation  —  White 
Precipitate  —  Zinc-Lead  Couple  —  Copper  in  Solution  —  Mer- 
cury in  Solution  —  Cutting  of  Zinc  Shavings  —  Mechanical  and 
Chemical  Consumption  of  Zinc  —  Regeneration  of  Cyanide  and 
Alkalinity  —  Zinc  Dust  Precipitation. 

CHAPTER  XIII 
CLEANING  -UP 176-178 

CHAPTER  XIV 

ROASTING  AND  ACID  TREATMENT , 179-183 

Roasting  —  Acid  Treatment  —  Sulphuric  Acid  Treatment  —  Sul- 
phurous Acid  Treatment  —  Bisulphate  of  Sodium  Treatment. 

CHAPTER  XV 

FLUXING  AND  MELTING 184-196 

Constituents  of  Zinc  Slime  to  be  Melted  —  Purpose  of  Fluxing 
and  Smelting  —  Sodium  and  Potassium  Carbonates  as  Fluxes  — 
Borax  and  Borax  Glass  as  Fluxes  —  Silica  as  a  Flux  —  Fluor  Spar 
as  a  Flux  —  Niter  as  a  Flux  —  Manganese  Dioxide  as  a  Flux  — 
Determining  the  Flux  to  be  LTsed  —  Variation  Due  to  Zinc  and 
the  Use  of  Oxidizers  —  General  Variations  and  Fluxing  Proced- 
ure —  Matte  Formation  —  Annealing  of  Graphite  Crucibles  — 


x  CONTENTS 

PAGES 

Melting  Furnaces  —  Preparation  of  Precipitate  and  Flux  —  Melt- 
ing Procedure  —  Treatment  of  Slag  and  Crucibles  —  Treatment  of 
Matte  —  Smelting  with  Litharge  and  Cupellation  —  Assay  of  Zinc 
Precipitate. 

CHAPTER  XVI 

CYANIDATION  OF  CONCENTRATE 197-204 

Treatment  by  Percolation  —  Treatment  by  Agitation  and  Fine- 
Grinding  —  General  Considerations. 

CHAPTER  XVII 
ROASTING  ORE  FOR  CYANIDATION 205-206 

CHAPTER  XVIII 

CYANIDE  POISONING 207-212 

Internal  Poisoning  —  Treatment  by  Hydrogen  Peroxide  —  Treat- 
ment by  Cobalt  Solution  —  Treatment  by  Ferrous  Salts  —  Poison- 
ing in  Precipitate  Refining  —  Prevention  of  Poisoning. 

CHAPTER  XIX 

CLASSIFIED  BIBLIOGRAPHY 213-269 

Books  —  History  and  Progress  —  Chemistry  and  Physio-chem- 
istry of  Cyanidation  —  Aeration  and  Oxidation  —  Commercial 
Cyanide  and  Its  Analysis  —  Analytical  Chemistry  of  Cyanide 
Solution  —  Assaying,  Samplers,  and  Sampling  —  Ore  Testing  and 
Physical  Tests  —  Alkalinity  and  Lime  —  Classification,  Dewater- 
ing,  and  Settlement  —  Sand  Treatment  and  Percolation  —  Slime 
Treatment,  Agitation,  and  Decantation  —  Filtration  —  Precipi- 
tation —  Cleaning-up,  Refining,  and  Melting  —  Telluride  Ore, 
Roasting,  Bromocyanide,  and  Chlorination  —  Cupriferous  Ore  and 
Solution  —  Concentrate  Cyanidation  —  Other  Refractory  Ores — • 
Cyanide  Poisoning  —  Construction,  Pulp  and  Residue  Conveying 
and  Disposal  —  Tube-Milling  and  Fine-Grinding  —  Cyanidation 
of  Silver  Ores,  and  in  Mexico  —  Cyanidation  in  United  States  and 
Canada  —  Cyanidation  in  South  Africa  —  Cyanidation  in  Aus- 
tralia —  Miscellaneous. 

CHAPTER  XX 

TABLES 269-281 

Metric  System  with  Conversions  —  United  States  Weights  and 
Measures  —  English,  Mexican,  and  United  States  Money  —  Value 
of  Gold  —  Conversion  of  Thermometer  Readings  —  Weight  and 
Measure  of  Water  —  Weight  of  Rock  and  Sand  —  International 
Atomic  Weights  (1911) —  Maximum  Solubilities  —  Formula?  for 
Circles  and  Circular  Tanks  —  Capacity  of  Circular  Tanks  — 
Slime  Pulp  Table. 

INDEX..  283 


TEXT  BOOK 
OF  CYANIDE  PRACTICE 


CHAPTER  I 
HISTORY  AND   DEVELOPMENT 

THE  cyanide  process  for  the  extraction  of  gold  and  silver  from 
their  ores  is  based  on  the  facts  that  a  very  dilute  cyanide  solu- 
tion will  dissolve  the  precious  metals  from  the  ore,  and  that 
when  this  enriched  solution  is  brought  into  contact  with  finely 
divided  zinc,  the  gold  and  silver  will  be  precipitated  so  that  it 
may  be  collected  and  melted  into  a  bar  of  bullion. 

Discovery  and  Early  Use  of  Cyanide.  —  Prussian  blue,  the 
first  cyanide  compound  known,  was  discovered  in  1704.  In 
1782  it  was  first  dimly  noted  that  a  cyanide  solution  would  dis- 
solve gold  and  silver.  During  the  succeeding  years  many  dif- 
ferent compounds  of  cyanide  were  determined  and  something 
of  their  properties  learned.  The  first  patent  on  the  solubility 
of  gold  in  cyanide  solution  was  taken  out  in  Great  Britain  in 
1840,  and  led  to  the  use  of  cyanide  solution  for  dissolving  gold 
and  silver  for  electroplating  purposes.  In  1844  Eisner  published 
valuable  investigations  regarding  the  solubility  of  gold  and  silver 
in  cyanide  solution. 

The  first  patent  purporting  to  use  a  cyanide  solution  for  dis- 
solving gold  and  silver  from  their  ores  was  taken  out  in  the 
United  States  by  J.  H.  Rae  in  1867.  Later  on  several  somewhat 
similar  patents  were  issued,  the  most  important  one  being  to 
J.  W.  Simpson  in  1885.  In  this  last  patent,  cyanide  of  potassium 
was  to  be  used  in  connection  with  other  chemicals  for  extract- 
ing gold,  silver,  and  copper  from  their  ores;  while  the  metals 
were  to  be  precipitated  from  the  solution  on  zinc  plates,  and 
obtained  therefrom  by  scraping  the  plates  or  dissolving  them 
in  sulphuric  or  hydrochloric  acid.  Electroplaters  were  at  this 

1 


2  TEXT  BOOK   OF   CYANIDE   PRACTICE 

time  making  use  of  zinc  to  recover  gold  and  silver  from  cyanide 
solution. 

.  Cyanide  of  potassium  was  also  being  used  to  a  very  limited 
extent  at  this  time  in  the  amalgamation  of  gold  ores,  being  intro- 
duced into  the  stamp-mill  mortar,  grinding  pan,  or  other  crush- 
ing device  with  a  rather  vague  idea  that  it  would  increase  the 
amount  of  gold  amalgamated.  This  it  undoubtedly  did  by 
removing  any  film  of  grease  or  oxide  surrounding  the  grains  of 
gold  and  brightening  them  for  easier  amalgamation,  but  as  it 
also  may  have  caused  a  little  gold  to  be  dissolved  and  carried 
away  in  solution,  it  was  poor  practice.  However,  since  it  some- 
times caused  a  lower  tailing  and  any  shortage  of  gold  was  not 
noticed,  the  use  of  cyanide  of  potassium  in  this  way  had  some 
favor. 

MacArthur-Forrest  Process.  —  Though  the  attention  of  scien- 
tists and  metallurgists  had  been  drawn  to  the  solvent  action  of 
cyanide  compounds  on  gold  and  silver,  resulting  in  considerable 
experimentation,  the  various  experiments,  studies,  and  patents 
can  hardly  be  considered  as  a  prologue  to  the  discovery  of  the 
present  cyanide  process,  or  as  having  a  direct  bearing  upon  it. 

In  1886  extended  experiments  were  being  carried  out  in 
Glasgow,  Scotland,  by  J.  S.  MacArthur,  R.  W.  Forrest,  and  W. 
Forrest,  for  the  purpose  of  developing  an  incipient  gold-extract- 
ing process.  In  the  course  of  their  experiments,  tests  were 
made  with  all  the  known  solvents  of  gold,  and  it  was  found  that 
a  solution  of  cyanide  of  potassium  gave  a  high  extraction  with  a 
small  consumption  of  the  chemical.  Their  first  application  for 
patent  covering  the  dissolving  power  of  cyanide  was  made  in 
Great  Britain  in  1887.  The  principal  detail  and  then  novel 
feature  was  the  low  strength  of  solution  to  be  used.  The  dis- 
coverers next  turned  their  attention  to  winning  the^old  from  the 
solution,  resulting  in  a  patent  being  taken  out  on  the  use  of 
zinc  in  a  state  of  fine  division,  such  as  in  the  form  of  shavings  or 
threads,  for  the  precipitation  of  the  gold  from  the  solution. 
Their  patents  also  included  the  use  of  caustic  alkalis  to  neutralize 
the  cyanide-destroying  acidity  of  the  ore,  which  involved  no 
new  idea  or  detail. 

Following  these  experiments  of  MacArthur-Forrest,  practical 
and  successful  applications  of  the  process  were  made  with  sur- 
prising rapidity  in  all  parts  of  the  world.  This  was  mainly  due 


HISTORY  AND  DEVELOPMENT  3 

to  the  inherent  virtue  and  applicability  of  the  process  and  to  the 
fact  that  the  syndicate  under  whose  direction  Mac  Arthur-Forrest 
developed  the  process,  trained  a  force  of  chemists  and  sent  them 
into  the  principal  gold-bearing  regions  of  the  world.  The  first 
plant  on  a  commercial  scale  was  established  at  Karangahake, 
New  Zealand,  in  1889.  In  South  Africa  the  first  plant  was  in- 
stalled near  Johannesburg,  Transvaal,  in  1890.  Both  of  these 
plants  were  established  under  the  direction  of  the  owners  of  the 
patents.  The  first  application  of  the  process  in  America  was 
made  at  Mercur,  Utah,  as  a  result  of  experiments  instigated  by 
the  reports  of  the  success  being  attained  in  Africa  and  Australia. 

Development  of  the  Cyanide  Process.  —  The  first  material 
treated  by  the  cyanide  process  was  mill  tailing  taken  from  the 
ponds  or  banks  in  which  they  had  accumulated,  and  treated  by 
the  leaching  process.  Then  quickly  followed  the  direct-filling 
method  of  conducting  the  tailing  flow  from  the  mill  to  revolving 
distributors  operating  similar  to  a  revolving  garden  sprinkler, 
and  known  from  its  inventors  as  the  Butters  and  Mein  distrib- 
utor. This  distributor  was  placed  over  a  leaching  vat  and  oper- 
ated to  fill  the  vat  with  sand  containing  some  slime,  the  major 
portion  of  the  slime  overflowing  the  rim  of  the  vat.  It  was 
found  that  the  sand  charge  was  not  easily  leached  owing  to  the 
amount  of  slime,  and  this  led  to  the  double-treatment  system 
in  which  the  sand  is  transferred  in  a  drained  condition  from 
the  collecting  vat  to  a  leaching  and  final-treatment  vat.  This 
method  was  perfected  on  the  South  African  Rand,  and  was 
followed  by  the  development  there  between  1894  and  1896  of 
the  decantation  process  of  slime  treatment  by  J.  R.  Williams. 
In  this  process  the  settled  and  dewatered  slime  is  diluted  and 
agitated  with  several  times  its  weight  of  cyanide  solution  until 
the  gold  and  silver  are  dissolved,  when  the  slime  is  allowed  to 
settle  and  the  supernatant  clear,  rich  solution  siphoned  off; 
after  which  the  slime  is  washed  free  of  the  dissolved  metals 
by  being  again  diluted,  agitated,  settled,  and  the  clear  solution 
drawn  off,  these  washings  being  continued  as  long  as  profitable. 

About  1898  the  filter-press  method  of  slime  treatment  was 
introduced  in  Australia  by  Sutherland,  where  it  has  been  exten- 
sively and  very  successfully  used.  In  America  the  filter  press 
was  used  to  only  a  limited  extent  up  to  the  introduction  of  the 
leaf  or  vacuum  filter,  previous  to  which  slime  treatment  was 


4      TEXT  BOOK  OF  CYANIDE  PRACTICE 

mainly  by  the  decantation  process.  Filter  presses,  with  the 
exception  of  the  Merrill  type,  have  fallen  into  disuse  in  America 
since  the  introduction  of  the  vacuum  filter.  In  the  standard 
filter-press  method  the  slime,  after  being  agitated  in  cyanide 
solution  until  the  precious  metals  are  dissolved,  is  forced  into  a 
plate-and-frame  filter  press.  After  the  press  is  full  of  slime,  the 
dissolved  metals  are  washed  out  of  the  slime  by  water  or  solution 
under  pressure,  when  the  press  is  opened  and  the  cakes  or  plates 
of  slime  are  dropped  into  a  car  or  sluice  for  the  waste  dump. 

The  first  practical  vacuum  or  suction  filter,  often  called  the 
leaf  filter,  was  devised  in  the  United  States  by  Moore  in  1903. 
In  this  method  a  leaf  consisting  of  a  flat  canvas  slip  or  pocket 
stretched  over  a  suitable  frame  is  immersed  in  the  slime  pulp  and 
a  suction  applied  to  the  interior  of  the  leaf,  causing  the  slime  to 
be  drawn  against  it,  and  the  solution  within.  This  action  in- 
duces a  leathery  coating  or  cake,  one-half  to  three  inches  thick, 
to  form,  when  the  leaf  with  its  cake  is  separated  from  the  excess 
pulp  and  brought  into  contact  with  a  wash  solution  or  water, 
which  washes  the  dissolved  "metal  out  of  the  cake  by  being 
drawn  by  the  suction  or  vacuum  through  the  slime  cake  into  the 
interior  of  the  leaf,  to  run  into  a  suitable  tank  to  which  the  leaf 
is  connected;  after  which  the  wash  solution  is  removed  and  the 
cake  is  discharged. '  In  some  of  these  filters  the  cake  is  formed 
and  washed  by  direct  mechanical  pressure  on  the  pulp  and  wash 
solution,  and  not  through  atmospheric  pressure  by  the  produc- 
tion of  a  suction  or  vacuum  in  the  interior  of  the  leaf.  The  best- 
;known  vacuum  and  pressure  leaf  filters  are  the  Butters,  Moore, 
Kelly,  Burt,  Ridgeway,  and  Oliver. 

--The  development  and  use  of  leaf  filters  has  marked  a  period 
in  which  fine-grinding  and  all-sliming  of  ore,  crushing  in  cyanide 
solution,  and  the  treatment  of  silver  and  other  ores  heretofore 
giving  a  low  extraction  has  been  rapidly  developed,  especially  in 
America.  Fine-grinding  had  to  some  extent  been  practiced  in 
connection  with  the  use  of  the  plate-and-frame  filter  press,  the 
tube  mill  having  been  introduced  by  Diehl  and  by  Sutherland 
in  Australia  in  1896  and  1898.  Crushing  in  solution  had  been 
carried  on  with  questionable  success  at  a  few  plants  since  early 
in  the  history  of  the  cyanide  process,  the  first  attempt  being  by 
Paul  in  northern  California  in  1891,  and  later  by  others  in  the 
Black  Hills.  But  it  is  only  since  the  introduction  of  leaf  filters 


HISTORY  AND  DEVELOPMENT  5 

that  fine-grinding  and  crushing  in  solution  has  become  generally 
practicable  and  desirable. 

Dry-crushing  for  cyanidation  was  rapidly  developed  during 
the  early  days  of  the  process,  but,  since  the  introduction  of  leaf 
niters  and  fine-grinding,  has  fallen  into  disuse,  except  where 
coarse  crushing  is  permissible.  Roasting  as  a  preliminary  to 
cyaniding  has  practically  disappeared,  except  for  sulphotelluride 
ores,  to  which  it  was  first  applied  in  1895.  The  discovery  that 
bromine  together  with  cyanide  as  a  bromocyanide  was  a  more 
active  solvent  or  a  supersolvent  of  the  precious  metals,  and 
its  application,  date  from  1892.  It  has  been  extensively  and 
successfully  used  in  the  treatment  of  sulphotelluride  ores  in 
Australia,  but  its  use  elsewhere  has  been  almost  unknown. 

The  electrical  precipitation  of  the  dissolved  metals  from 
cyanide  solution  was  introduced  in  South  Africa  in  1893,  and 
great  importance  was  attached  to  it.  However,  it  has  been  al- 
most entirely  abandoned,  though  used  in  a  few  isolated  instal- 
lations to-day.  Electrical  precipitation  without  removing  the 
solution  from  the  pulp  has  never  been  a  commercial  success. 

The  use  of  zinc  dust  as  a  precipitant  in  place  of  shavings 
dates  from  1894.  It  has  been  in  favor  in  many  large  plants, 
but  only  during  the  last  few  years  has  there  been  a  tendency 
to  consider  it  preferable  to  the  standard  zinc  shavings,  and  then 
mainly  in  America. 

Some  of  the  early  experiments  made  by  MacArthur-Forrest, 
and  of  the  first  work  in  actual  practice,  were  done  upon  sulphide 
or  mill  concentrate,  but  the  cyanidation  of  this  material  may  be 
said  to  be  only  partly  developed,  except  as  the  general  improve- 
ments of  the  cyanide  process  have  been  applied.  It  is  a  fertile 
field  for  improvement. 

The  fundamental  chemistry  of  cyanidation  was  fairly  well 
worked  out,  considering  the  numerous  and  complex  reactions 
that  take  place,  during  the  early  years  of  the  process.  The 
investigation  of  the  chemical  side  of  cyanidation  has  been  com- 
paratively slow  during  the  latter  years,  due  to  the  high  techni- 
cal and  scientific  ability  requisite  in  doing  such  work,  and  to  the 
fact  that  investigations  into  the  physical  and  mechanical  side 
have  been  much  more  profitable  individually,  and  have  so  com- 

tletely  occupied  the  time  and  attention  of  investigators  and 
perators  that  time  for  scientific  research  has  not  been  available. 


6      TEXT  BOOK  OF  CYANIDE  PRACTICE 

,  The  physical  and  mechanical  side  of  cyanidation  has  been  in 
a  state  of  continuous  development  since  the  first  introduction  of 
the  process,  and  the  field  is  now  wider  and  better  than  ever. 
The  proof  of  this  is  to  be  seen  in  the  widely  varying  methods 
of  leaching,  agitating,  filtering,  and  other  details  in  the  same 
locality,  and  the  still  wider  variations  in .  the  different  gold- 
silver  regions  of  the  world,  also  in  the  constant  introduction  of 
new  devices.  The  field  of  cyanidation  has  been  and  is  constantly 
widening  through  its  encroachment  upon  amalgamation,  concen- 
tration, and  smelting. 


CHAPTER  II 
NATURE  AND   PROPERTIES   OF   CYANIDE 

Definition  of  Cyanide  and  Cyanogen.  —  Cyanogen  is  the  com- 
pound radical  CN,  the  carbon  (C)  and  nitrogen  (N)  constituents 
of  hydrocyanic  acid  (HCN),  which  is  composed  of  hydrogen  (H), 
carbon,  and  nitrogen,  and  is  often  called  prussic  acid.  Cyanide 
is  a  compound  of  the  cyanogen  radical  CN  with  usually  a  metallic 
substance,  as  potassium  (K)  or  sodium  (Na),  forming  potassium 
cyanide  (KCN)  or  sodium  cyanide  (NaCN).  A  radical  in 
chemistry  may  refer  to  a  single  element,  in  which  case  it  is  a 
simple  radical,  but  more  often  refers  to  a  group  of  two  or  more 
elements,  which,  once  united,  thereafter  combine  in  chemical 
union  or  break  the  chemical  bonds  with  other  elements  or  com- 
pounds as  if  they  were  a  single  element  incapable  of  being  dis- 
associated into  two  or  more  elements.  The  radical  cyanogen 
(CN),  or  cyanide  radical,  is  composed  of  one  atom  of  carbon  (C) 
and  one  of  nitrogen  (N),  and  in  all  the  phases  of  the  cyanide 
process  and  its  chemistry  this  chemical  union  is  never  broken. 
To  do  so  would  be  to  lose  the  solvent  action  on  the  metals,  for 
neither  carbon  nor  nitrogen  has  any  such  dissolving  effect.  Nei- 
ther is  there  much  tendency  for  the  two  elements  to  disassociate. 
While  the  chemical  symbol  for  cyanogen,  or  the  cyanide  radical, 
is  CN,  it  has  become  a  custom  to  write  it  Cy,  a  contraction  of 
cyanide. 

Properties  and  Reactions  of  Cyanide  and  Cyanogen.  —  Cyano- 
gen is  a  colorless  gas  and  does  not  exjst  free  to  any  extent,  con- 
sequently it  must  be  fixed  by  being  combined  with  a  metal  or 
other  substance  to  hold  it.  It  is  a  most  active  radical,  especially 
in  combining  with  the  metals,  with  which  it  forms  several  hundred 
compounds,  thus  increasing  the  difficulty  in  isolating  and  deter- 
mining the  properties  of  each,  more  especially  under  working 
conditions,  —  a  fact  that  has  hindered  the  investigations  of  the 
chemistry  of  the  cyanide  process.  Cyanogen,  or  the  cyanide 
radical,  is  related  to  the  cyanides  as  chlorine  is  related  to  the 

7 


8      TEXT  BOOK  OF  CYANIDE  PRACTICE 

chlorides,  and  iodine  to  the  iodides.  As  the  acid  radical  864  of 
sulphuric  acid  (H2S04)  unites  with  iron  (Fe)  to  form  an  iron 
sulphate  (FeS04),  and  the  acid  radical  Cl  of  hydrochloric  acid 
(HC1)  unites  with  iron  to  form  an  iron  chloride  (FeCl2),  so  does 
the  cyanide  radical  CN  unite  with  iron  to  form  primarily  an 
iron  cyanide  (Fe(CN)2),  and  similarly  with  other  metals.  The 
result  of  the  chemical  combination  of  the  radical  CN  with  a 
base  or  metal  is  to  form  a  salt,  such  as  potassium  cyanide  (KCN 
or  KCy)  or  sodium  cyanide  (NaCN  or  NaCy).  The  chemical 
principles  involved  in  the  formation  of  common  table  salt,  sodium 
chloride  (NaCl),  are  the  same  as  those  involved  in  the  formation 
of  sodium  cyanide  (NaCN). 

Cyanogen  combines  to  form  simple  or  single  cyanides,  which 
may  be  regarded  as  metals  replacing  the  H  of  HCN,  as: 


and  to  form  double  cyanides  which  may  be  considered  as  a  com- 
bination of  two  single  cyanides,  as: 

Zn(CN)2  +  2  KCN  =  K2Zn(CN)4, 

in  which  the  zinc  cyanide  (Zn(CN)2)  first  formed  between  zinc 
and  cyanide  and  the  potassium  cyanide  are  the  single  cyanides, 
and  the  potassium  zinc  cyanide  (K2Zn(CN)4)  finally  formed  is 
the  double  cyanide.  Other  and  more  complex  cyanogen  com- 
pounds form  and  are  found  under  working  conditions. 

The  metal  or  base  with  which  cyanogen  is  combined  to  form 
a  cyanide  is  easily  replaced  by  one  for  which  cyanogen  has  a 
greater  affinity.  Thus  in  a  KCN  solution  the  K  is  replaced  by 
gold  (Au),  forming  the  simple  cyanide  AuCN,  and  finally  the 
double  cyanide  KAu(CN)2,  because  cyanogen  has  a  greater 
affinity  for  gold  than  for  potassium  (K).  When  the  solution 
containing  a  gold  cyanide  is  brought  into  contact  with  zinc  (Zn), 
the  gold  is  replaced  by  the  zinc  owing  to  the  greater  affinity  of 
cyanogen  for  zinc  than  for  gold,  the  reaction  being: 

2  KAu(CN)2  +  Zn  =  K2Zn(CN)4  +  2  Au. 

It  is  the  action  of  this  principle  that  makes  the  cyanide  process 
for  gold  and  silver  extraction  possible. 

Cyanogen  Used  in  the  Cyanide  Process.  —  The  sources  of 
cyanogen  in  the  cyanide  process  are  potassium  cyanide  and 
sodium  cyanide,  the  simple  cyanides  of  the  alkaline  metals  potas- 


NATURE  AND  PROPERTIES  OF  CYANIDE    9 

slum  and  sodium.  There  are  other  simple  cyanides  of  the  alka- 
line earths  and  metals,  such  as  ammonium  cyanide  (NH2CN), 
barium  cyanide  (Ba(CN)2),  calcium  cyanide  (Ca(CN)2),  mag- 
nesium cyanide  (Mg(CN)2),  and  strontium  cyanide  (Sr(CN)2). 
These  have  solvent  powers  similar  to  those  of  potassium  and 
sodium  cyanide,  but  are  not  used  in  the  ordinary  cyanide  process, 
mainly  for  economic  reasons.  The  double  cyanides  have  con- 
siderable solvent  power  in  some  cases,  but  are  too  stable  and 
hold  their  cyanogen  too  firmly  to  be  a  source  of  it,  except  so  far 
as  it  is  possible  to  utilize  that  formed  in  working  solutions.  The 
other  and  complex  cyanogen  compounds  have  little  or  no  dis- 
solving effect. 

Potassium  cyanide  is  a  white  salt  with  the  usual  salty  taste. 
It  gives  an  alkaline  reaction  and  is  easily  dissolved  and  very 
soluble  in  water.  One  part  of  boiling  water  will  dissolve  1.2 
parts  of  the  salt.  Exposed  to  the  atmosphere,  especially  in  the 
presence  of  moisture,  there  is  a  slight  decomposition  into  hydro- 
cyanic acid  sufficient  to  give  the  characteristic  odor  similar  to 
that  of  an  almond  or  peach  kernel  and  irritating  to  the  mucous 
membrane.  It  is  an  irritant  to  the  skin  externally  and  a  deadly 
poison  internally.  Sodium  cyanide  has  almost  identical  prop- 
erties. The  salts  are  made  by  fusing  nitrogenous  substances, 
as  horns,  hoofs,  dried  blood,  old  leather,  etc.,  with  alkali  and 
iron,  followed  by  a  refining  or  eliminating  process,  leaving  the 
desired  salt;  or  by  synthetic  processes  fixing  nitrogen  from  the 
atmosphere  or  ammonia  by  passing  them  over  heated  alkaline 
salt  and  carbon  to  form  a  union  of  the  carbon,  nitrogen,  and 
sodium  or  potassium  as  sodium  or  potassium  cyanide. 

Difference  between  Sodium  and  Potassium  Cyanide.  - 
Practically  the  only  difference  between  sodium  and  potassium 
cyanide,  and  in  the  main  with  the  other  simple  alkaline  cyanides, 
is  the  dissolving  strength,  which  depends  upon  the  amount  of 
the  CN  radical.  The  atomic  weight  of  potassium  is  39.1,  of 
sodium  is  23,  of  carbon  is  12,  and  of  nitrogen  is  14.  Consequently 
the  weight  of  a  molecule  of  potassium  cyanide  is: 

K          c        N 
39.1  +12  +  14  =65.1, 

of  which  the  cyanogen  (CN)  represents  26  of  the  total  65.1  parts 
by  weight,  which  is  40  per  cent  or  40  parts  CN  in  100  of  the  salt. 
The  weight  of  a  molecule  of  sodium  cyanide  is  in  a  similar  way: 


10  TEXT  BOOK  OF  CYANIDE  PRACTICE 

Na          C  N 

23  +  12  +  14  =  49, 

of  which  the  cyanogen  represents  26  parts  of  the  total  49  parts 
by  weight,  which  is  53.06  per  cent  or  53.06  parts  CN  in  100  of 
the  salt.  If,  in  equal  weights  of  the  salt,  potassium  cyanide  con- 
tains 40  parts  CN  and  sodium  cyanide  contains  53.06,  then  the 
dissolving  strength  of  sodium  cyanide  is  1.3265  times  that  of 
potassium,  or  it  is  132.65  per  cent  strong  when  the  pure  potassium 
salt  is  considered  as  100  per  cent  strength.  This  method  of 
considering  pure  potassium  cyanide  as  100  per  cent  strong  and 
marking  all  cyanide,  whether  potassium  or  sodium  and  pure  or 
impure,  according  to  its  strength  or  amount  of  CN  radical  as 
compared  with  pure  potassium  cyanide  at  100  per  cent,  is  now 
in  practice  everywhere. 

It  is  impossible  to  say  which  of  the  two  salts  is  the  better  for 
use  in  cyanide  work.  Potassium  cyanide  was  at  first  used  en- 
tirely, apparently  because  it  was  the  only  salt  available.  In 
recent  years  sodium  cyanide  has  been  extensively  used  and  has 
met  with  considerable  favor  at  some  plants,  while  others  have 
found  it  unsatisfactory  and  have  preferred  to  return  to  the  use 
of  potassium  cyanide.  Sodium  cyanide,  whether  in  the  solid 
form  or  in  solution,  appears  to  be  less  stable  and  consequently 
to  decompose  faster  than  potassium  cyanide.  In  wet  climates 
it  absorbs  moisture  faster  and  gives  some  trouble  in  this  way 
through  deliquescing.  Its  base,  sodium,  forms  more  soluble 
compounds  than  the  potassium  of  potassium  cyanide,  and  may 
give  trouble  by  precipitating  them  in  the  zinc  boxes.  Com- 
mercial cyanide  is  generally  far  from  being  pure,  owing  to  alka- 
line constituents  that  are  introduced  in  the  process  of  manu- 
facture. Potassium  cyanide  may  often  contain  considerable  of 
the  stronger  sodium  cyanide,  introduced  for  the  purpose  of  bring- 
ing it  up  to  the  branded  strength.  The  effect  of  these  impur- 
ities, like  any  difference  between  pure  potassium  and  sodium 
cyanide,  is  not  well  understood,  but  is  being  studied,  and  prob- 
ably will  result  in  requiring  cyanide  of  a  certain  purity  and  com- 
position. This  will  be  an  improvement  of  the  method  in  the  past 
of  purchasing  the  most  economical  salt  as  determined  by  calcula- 
tions based  on  the  branded  strength  and  the  cost  of  the  cyanogen 
(CN)  delivered  at  the  plant;  the  higher  strength  salt  often  being 
more  economical  owing  to  the  indirect  saving  in  transportation. 


CHAPTER  III 
DISSOLUTION   OF   GOLD   AND   SILVER 

Reactions.  —  It  is  generally  accepted  that  gold  is  dissolved 
by  a  cyanide  solution  in  accordance  with  the  equation  first 
brought  to  public  attention  by  Eisner  and  known  as  Eisner's 
equation: 

2Au  +  4  KCN  +  0  +  H20  =  2KAu(CN)2  +2KOH; 

the  gold  (Au)  combining  with  potassium  cyanide  (KCN), 
oxygen  (O),  and  water  (H2O)  to  form  a  gold  potassium  cyanide 
(KAu(CN)2)  and  caustic  potash  (KOH).  The  simple  gold 
cyanide  (Au(CN))  is  probably  first  formed  to  be  changed  into 
the  double  gold  cyanide  (KAu(CN)2),  as: 

2  Au  +  2  KCN  +  O  +  H2O  =  2  Au(CN)  +  2  KOH. 

Au(CN)  +  KGN  =  KAu(CN)2. 
Silver  is  dissolved  in  a  way  similar  to  gold,  as : 

2  Ag  +  4  KCN  +  O  +  H2O  =  2  KAg(CN)2  +  2  KOH. 

One  part  of  potassium  cyanide  should  dissolve  1.51  parts  of 
gold  or  .83  part  of  silver  according  to  the  above  formula?. 

Necessity  and  Source  of  Oxygen.  —  It  is  seen  from  the  above 
equations  that  oxygen  is  necessary  in  dissolving  gold  and  silver. 
This  has  been  confirmed  in  experiments  and  practice.  The 
necessary  oxygen  is  supplied  by  the  air  or  oxygen  which  the  solu- 
tion has  absorbed  through  being  exposed  to  the  atmosphere,  and 
by  that  absorbed  or  held  by  the  ore  itself.  Oxygen  may  also  be 
supplied  by  pumping  air  through  the  charge  or  solution,  or  by 
chemical  oxidizers.  However,  it  has  been  abundantly  proven 
in  practice  that  the  attempt  to  supply  oxygen  artificially  soon 
reaches  a  point  where  it  is  uneconomical.  Consequently  the 
necessary  supply  of  oxygen  is  relied  upon  to  be  had  by  the  use 
of  a  sufficiently  large  volume  of  freshly  precipitated  and  aerated 
solution,  by  aerating  the  ore  through  draining  and  drawing  the 

11 


12  TEXT  BOOK  OF  CYANIDE  PRACTICE 

atmosphere  into  the  interstices  between  the  grains  of  pulp,  by 
bringing  the  pulp  into  contact  with  the  atmosphere  when  agitat- 
ing, by  agitating  with  compressed  air,  and  in  exceptional  cases 
by  pumping  or  drawing  air  through  the  charge.  The  necessit.y 
of  providing  much  oxygen  by  stress  on  these  means  is  small  with 
a  clean,  gold  ore,  but  increases  with  the  quantity  of  sulphide  or 
baseness  of  the  ore,  and  with  most  silver  ores,  since  the  metallic 
compounds  of  these  ores  decompose  or  oxidize  to  form  new 
compounds,  thereby  utilizing  or  abstracting  the  oxygen  neces- 
sary in  the  dissolution  process.  The  best-known  chemical  oxi- 
dizers  that  may  be  used  are  sodium  peroxide  (Na2O2),  potassium 
permanganate  (KMnO4),  and  manganese  dioxide  (Mn02).  While 
these  hasten  the  dissolution,  they  have  never  been  found  to  be 
of  economic  value,  as  they  invariably  do  not  give  any  increased 
extraction  over  that  which  can  be  obtained  by  using  a  little  more 
time  or  more  aeration  of  the  charge  and  solution. 

Bromocyanide  and  Mercury  Salts  as  Super  solvents.  —  The 
dissolving  power  of  cyanide  solution  has  been  increased  by  the 
addition  of  chemicals  which  have  something  of  an  oxidizing 
effect,  but  act  mainly  through  the  liberation  of  cyanogen  in  a 
nascent  state  —  ready  and  strongly  desirous  of  uniting  with  a 
substance  replacing  the  H  of  HCN.  Bromine  in  connection 
with  cyanide  as  bromocyanide  is  the  only  chpmical  that  has  been 
used  to  any  extent  for  this  purpose,  and  then  only  on  telluride 
and  sulphide  ores  that  will  not  give  a  good  extraction  otherwise. 
Its  use  requires  such  care  and  expense  that  it  is  undesirable  for 
treating  ores  from  which  a  good  extraction  can  be  secured  other- 
wise by  the  usual  processes.  The  reactions  that  occur  in  the 
use  of  bromocyanide  have  never  been  solved,  but  the  super- 
solvent  qualities  are  presumed  to  be  due  to  the  liberation  of 
nascent  cyanogen  and  to  some  oxidizing  effect,  since  the  bromine 
does  not  enter  into  combination  with  the  gold. 

Mercurous  (Hg2Cl2)  or  mercuric  chloride  (HgCl2)  has  been 
added  as  a  chemical  in  addition  to  the  cyanide  used.  Its  effect 
appears  to  be  due  to  the  affinity  of  mercury  for  cyanogen,  form- 
ing a  mercuric  cyanide  (Hg(CN)2)  or  a  double  mercuric  cyanide 
of  potassium  (K2Hg(CN)4),  by  decomposing  such  stable  com- 
pounds as  the  ferrocyanides  and  ferricyanides  (K4Fe(CN)6  and 
K3Fe(CN)6)  in  addition  to  the  simple  cyanides  and  easily- 
decomposed  double  cyanides,  thus  removing  the  interference  of 


DISSOLUTION  OF  GOLD  AND  SILVER  13 

the  ferrocyanides.  The  double  mercuric  cyanide  dissolves  gold 
and  silver  without  requiring  oxygen,  as : 

K2Hg(CN)4  +  2  Au  =  2  KAu(CN)2  +  Hg. 
From  the  silver  sulphide  the  dissolution  may  proceed  as: 

K2Hg(CN)4  +  AgaS  =  2  KAg(CN)2  +  HgS. 

The  mercuric  sulphide  (HgS)  formed  being  stable  and  insoluble, 
and  therefore  not  a  detriment  as  the  alkaline  sulphide  (K2S) 
formed  when  the  silver  sulphide  is  acted  upon  by  KCN,  as : 

4  KCN  +  AggS  =  2  KAg(CN)2  +  K2S. 

The  alkaline  sulphide  being  an  abstractor  of  oxygen  unless 
altered  into  an  insoluble  and  stable  sulphide,  as  the  mercuric 
sulphide  (see  Alkaline  Sulphides  and  Sulphocyanides).  The 
mercury  salts  have  been  used  to  a  slight  extent  in  this  way  in 
the  working  of  sulphide  silver  ores. 

Strength  of  Solution  Required.  —  The  strength  of  solution 
required  varies.  Experimental  work  in  the  laboratory  will  indi- 
cate the  most  advisable  strength  for  starting  a  new  ore  or  plant. 
But  this  strength  is  invariably  reduced  in  the  course  of  time,  due 
to  the  desirableness  of  starting  new  operations  with  a  sufficiently 
strong  solution,  and  that  a  cyanide  solution  after  being  in  use 
for  some  time  is  found  to  contain  cyanogen  compounds  that  are 
not  apparent  in  the  usual  test  for  cyanide  strength,  but  which 
have  a  direct  or  indirect  solvent  effect. 

Experiments  have  shown  that  both  pure  gold  and  silver  dis- 
solve most  rapidly  in  a  solution  of  .25  per  cent  (5  pounds  per  ton 
of  solution)  KCN,  that  between  .1  per  cent  (2  pounds)  and  .25 
per  cent  (5  pounds)  the  dissolving  rate  is  nearly  constant,  but 
grows  less  with  solutions  above  or  below  these  strengths.  The 
lessened  efficiency  of  cyanide  solutions  stronger  than  .25  per  cent 
(5  pounds)  KCN  in  the  above  experiments  is  ascribed  to  the  fact 
that  the  amount  of  oxygen  soluble  in  a  solution  grows  less  as  its 
cyanide  content  becomes  greater.  When  oxygen  is  supplied  as 
needed,  a  stronger  solution  will  dissolve  the  metals  faster  than  a 
weak  one,  but  the  weaker  the  solution  the  more  highly  efficient 
equal  amounts  of  cyanide  will  be,  and  the  less  will  be  the  cyanide 
consumption  per  ton  of  ore  treated  or  unit  of  precious  metals 
dissolved. 

The  present  practice  in  leaching  an  ore  containing  gold  that 


14  TEXT  BOOK  OF  CYANIDE  PRACTICE 

is  easily  dissolved  is  to  use  about  a  .1  per  cent  (2  pounds)  KCN 
solution,  and  seldom  higher  than  .2  per  cent  (4  pounds);  while 
in  the  agitation  treatment  of  such  ores,  solutions  from  .05  per 
cent  (1  pound)  to  .1  per  cent  (2  pounds)  are  generally  used. 
On  silver  ores  a  .1  per  cent  (2  pounds)  to  .3  per  cent  (6  pounds) 
solution  is  usual  in  agitation,  and  from  a  .25  per  cent  (5  pounds) 
to  .5  per  cent  (10  pounds)  in  leaching  practice.  For  treating 
concentrate  by  agitation,  solutions  ranging  from  .15  per  cent 
(3  pounds)  to  .4  per  cent  (8  pounds)  are  in  use,  and  from  .2  per 
cent  (4  pounds)  to  .75  per  cent  (15  pounds)  for  leaching.  To 
enable  the  stronger  solutions  to  act  most  efficiently  and  get  the 
increased  advantage  of  their  higher  strength,  it  is  necessary  to 
supply  plenty  of  oxygen,  which  the  method  of  operating  does 
by  aerating  the  solution  and  ore  frequently. 

The  use  of  a  stronger  solution  causes  a  higher  consumption  of 
cyanide  mainly  by  the  increased  effect  of  the  stronger  solution 
upon  the  base  metals  and  cyanicides.  This  action  upon  the 
base  metals  is  slow,  and  while  they  dissolve  according  to  their 
slower  rate  of  solubility  at  the  time  the  gold  and  silver  is  being 
dissolved,  their  dissolution  continues  as  vigorously  after  the 
comparatively  quick  dissolution  of  gold  and  silver  is  made;  con- 
sequently the  strong  or  dissolving  solution  should  be  withdrawn 
as  soon  as  the  precious  metals  are  dissolved,  and  the  weak  solu- 
tions used  thereafter  for  washing.  The  so-called  "  selective 
action  "  of  cyanide  in  dissolving  the  precious  metals  is  not  a  true 
selection  of  these  in  preference  to  the  base  metals,  but  is  due  to 
the  somewhat  quicker  dissolution  of  the  precious  metals  under 
equal  conditions,  and  to  the  fine  state  of  division  and  small 
amount  of  them  in  comparison  with  the  base  metals  —  conditions 
which  allow  comparatively  quick  and  easy  dissolution  of  the 
precious  metals. 

t/Cyanicides.  —  The  solubility  of  gold  and  silver  in  cyanide  solu- 
tions is  reduced  by  the  presence  of  "  cyanicides  "  in  the  ore.  A 
"  cyanicide  "  is  any  substance  outside  of  the  precious  metals 
and  those  involved  in  the  working  of  the  process  —  as  the  zinc — 
that  will  unite  chemically  with  the  cyanide  or  tend  to  decompose 
it,  thereby  destroying  the  cyanide  or  rendering  it  inert  for  dis- 
solving purposes.  Such  substances  may  be  a  mejbal,  as  copper 
(Cu)  or  iron  (Fe)  when  in  a  condition  to  be  acted  upon  by  a 
cyanide  solution,  such  as  in  the  form  of  a  salt,  producing  in  the 


DISSOLUTION  OF  GOLD  AND  SILVER  15 

case  of  copper  a  potassium  cuprous  cyanide  (K2Cu2(CN)4)  or  in 
the  case  of  iron  a  potassium  ferrocyanide  (K4Fe(CN)6).  Acids 
are  active  cyanicides,  forming  hydrocyanic  acid  (HCN)  with 
the  cyanogen.  Cyanicides  hinder  the  solubility  of  gold  and 
silver  in  two  ways:  first,  by  destroying  or  neutralizing  the 
cyanide  so  that  it  is  not  available  for  dissolving  the  gold  and 
silver;  and  second,  by  going  into  solution  to  such  an  extent 
that  the  solution  becomes  inactive  towards  the  dissolution  or 
precipitation  of  gold  and  silver,  in  which  condition  it  is  said  to  be 
"  foul."  The  action  of  cyanicides  is  met  by  removing  them 
from  the  ore  by  concentration,  water- washing,  etc.;  by  neutraliz- 
ing them  into  inert  salts  by  the  use  of  the  proper  quantity  of  lime, 
etc.,  —  including  aeration  —  introduced  into  the  ore  or  solution; 
by  the  passage  of  the  solution  through  the  zinc  boxes,  which  often 
appears  to  cleanse  it  of  the  influences  which  retard  its  dissolving 
effect;  and  by  keeping  the  solution  so  low  in  cyanide  strength 
that  it  will,  by  its  greater  affinity  or  dissolving  influence  on  gold 
and  silver,  —  its  selective  action  towards  them  —  dissolve  these 
metals  and  leave  the  base  metals  and  cyanicides  unacted  upon 
as  much  as  possible. 

Heating  the  Solution.  —  Laboratory  experiments  often  indi- 
cate that  a  higher  extraction  can  be  obtained  by  a  heated  solu- 
tion than  a  cold  one.  In  practice  it  has  generally  been  impossible 
to  notice  any  difference  between  the  normal  extraction  and  that 
made  by  heating  the  ore  and  solution,  or  that  obtained  during 
the  heat  of  summer  or  the  frigid  weather  of  winter.  A  few  cases 
have  been  reported  in  which  some  virtue  has  been  found  in  heat- 
ing the  solution.  However,  it  is  the  more  general  experience 
that  no  additional  extraction  is  obtained,  or  at  least  nothing 
sufficient  to  warrant  the  cost  of  heating  the  solution  and  the 
additional  consumption  of  cyanide  due  to  its  decomposition, 
and  the  increased  decomposition  and  resulting  activity  of  the 
base  metals  and  cyanicides;  though  the  decomposition  of  the 
base  metals,  compounds,  and  alloys  is  beneficial  in  liberating 
the  precious  metals,  that  they  may  be  more  easily  dissolved. 
One  reason  that  militates  against  the  use  of  a  heated  solution 
is  that  as  the  solution  is  heated  it  is  unable  to  retain  the  oxygen 
dissolved  in  it. 

Effect  of  Size  of  Metal  Particles.  —  The  size  and  shape  of  the 
particles  of  gold  and  silver  have  an  important  influence  on  their 


16  TEXT  BOOK  OF  CYANIDE  PRACTICE 

rate  of  solubility.  Where  the  metal  is  in  very  fine  particles,  it 
will  be  quickly  dissolved  and  require  only  a  weak  solution  to  get 
the  maximum  dissolution  within  a  reasonable  length  of  time. 
When  the  particles  are  large,  a  larger  surface  is  exposed  to  the 
action  of  the  solution,  causing  a  large  amount  of  metal  to  go  into 
solution  in  a  given  time.  Presuming  that  the  metal  is  in  spheres, 
the  solution  is  constantly  removing  a  film  of  metal  and  reducing 
the  spheres  to  smaller  diameters,  consequently  larger  spheres 
or  metal  in  thick  particles  will  require  considerable  time  for 
dissolution  over  that  necessary  when  the  same  amount  of  metal 
exists  in  thin  plates  or  in  a  larger  number  of  smaller  particles. 
In  practice,  ore  containing  the  metal  in  a  comparatively  coarse 
state,  not  removed  by  amalgamation  or  concentration,  needs  to 
be  treated  with  a  strong  dissolving  solution  to  reduce  the  time 
of  dissolution  to  that  of  an  ore  containing  finely-divided  metal 
treated  with  a  weak  and  more  slowly  solvent  solution. 

Effect  of  Crushing  and  Form  in  which  Metal  is  Held.  —  The 
crushing  must  either  liberate  the  gold  and  silver  from  its  matrix 
or  expose  a  face  of  it,  that  the  cyanide  solution  may  act  upon  it. 
Though  with  porous  ore,  that  the  solution  can  penetrate  and  be 
withdrawn  from,  it  is  not  so  essential  that  the  precious  metal 
be  liberated.  Following  the  above  principle,  various  factors 
affect  the  degree  of  fineness  to  which  the  ore  must  be  crushed. 
Where  the  gold  is  finely  divided  it  naturally  follows  that  fine 
crushing  will  be  required  to  liberate  it,  more  especially  with  hard 
dense  ores,  which  the  solution  cannot  penetrate.  When  the  gold 
is  comparatively  coarse,  a  face  may  be  exposed  by  coarse  crush- 
ing which  will  allow  dissolution  to  continue  slowly  inward,  until 
the  entire  amount  of  metal  is  eaten  out.  Sulphides  especially 
require  fine  grinding  to  liberate  the  gold  they  mechanically  hold. 
Many  ores  contain  the  gold  on  the  breaking  or  parting  planes, 
from  which  it  is  liberated  in  the  crushing  process  which  naturally 
splits  the  grains  along  these  planes,  or  the  solution  easily  pene- 
trates the  fractures.  Fine-grinding,  especially  of  a  sliming 
nature,  besides  liberating  the  particles  of  precious  metal,  also 
breaks  them  up  or  hammers  them  into  thin  particles  so  that  they 
are  quickly  dissolved  by  cyanide.  Whereas,  by  a  system  of 
crushing  that  only  liberates  the  metal,  considerable  time  for 
dissolution  would  be  required  by  the  larger  particles.  Sliming 
in  solution  is  especially  efficacious,  for  the  metals  are  ground  fine 


DISSOLUTION  OF  GOLD  AND  SILVER  17 

in  a  large  volume  of  well-aerated  solution  under  an  agitation  that 
is  very  favorable  for  causing  the  metals  to  go  into  solution. 
When  the  metals  exist  as  compounds,  as  gold  combined  with 
tellurium,  and  silver  with  sulphur,  chlorine,  etc.,  fine-grinding 
is  necessary  to  get  the  highest  efficiency  of  the  cyanide  solution 
in  attacking  the  compounds  and  removing  the  precious  metals, 
it  being  very  much  on  the  same  principle  as  gold  and  silver 
mechanically  held  or  more  or  less  alloyed  with  base  metals. 

Some  ores  may  only  require  crushing  to  J-  to  J-inch  cubes,  such 
as  low-grade,  porous,  friable  ores.  Others  may  give  good  ex- 
tractions only  when  crushed  to  a  200-mesh  or  even  finer.  The 
rule  may  be  given  that  the  harder,  denser,  higher-grade,  more 
sulphuretted,  and  baser  the  ore  is,  the  finer-grained  and  more 
tightly  held  mechanically,  combined,  or  alloyed  the  gold  and 
silver  is,  the  finer  will  be  the  crushing  required.  That  the  softer, 
more  leachable,  oxidized,  friable,  porous,  less  base,  and  lower 
grade  the  ore  is,  the  coarser  and  freer  that  the  gold  and  silver  is 
mechanically  and  otherwise  held,  the  coarser  will  be  the  crushing 
permissible  to  obtain  an  economic  extraction.  This  rule  is 
subject  to  the  effect  the  solution  will  have  upon  the  cyanicides, 
the  cost  of  crushing  and  grinding,  and  the  trouble  or  expense  and 
the  efficiency  in  handling  the  slime,  all  of  which  increase  with 
finer  crushing. 

Volume  of  Solution  Required  and  Method  of  Application.  — 
The  volume  of  solution  and  method  of  application  should  be  such 
that  the  solution  at  all  times  contains  sufficient  oxygen  and 
cyanide  strength  for  efficient  dissolution.  An  ore  containing 
cyanicides  that  destroy  the  cyanide  or  coarse  metal  that  con- 
sumes it  in  the  dissolving  process  will  require  leaching  or  agita- 
tion with  a  large  volume  of  solution  or,  less  preferably,  the 
addition  of  more  cyanide  during  the  agitation;  that  a  solution  of 
reasonable  dissolving  strength  may  be  always  available  about 
each  particle  of  metal,  and  yet  that  there  be  not  the  loss  due  to 
the  use  of  an  inordinately  high  cyanide  strength.  An  ore  con- 
taining reducing  or  deoxidizing  agents  rapidly  fouls  the  solution 
towards  dissolving  the  metals  by  abstracting  the  necessary 
oxygen,  to  remedy  which  the  charge  must  be  aerated  or,  as  is 
sometimes  more  convenient  and  desirable,  the  fouled  solution  is 
replaced  by  a  freshly-aerated  one.  Where  the  cyanicides  and 
reducing  agents  exert  themselves  in  this  way,  a  large  volume  of 


18  TEXT  BOOK  OF  CYANIDE  PRACTICE 

solution  is  required  and  is  applied  by  being  continuously  leached 
through  the  percolation  charge,  or  by  a  large  amount  of  solution 
in  comparison  to  the  dry  pulp  in  an  agitation  charge,  or  by  re- 
placing with  fresh  solution  through  settling  the  pulp  and  decant- 
ing off  the  old  solution.  The  distinction  between  that  solution 
required  to  dissolve  the  metals  and  that  required  to  wash  these 
dissolved  metals  out  of  the  ore  must  be  clearly  borne  in  mind, 
though  in  practice  the  functions  of  both  may  be  considered  as 
more  or  less  united.  With  an  ore  containing  easily  dissolved 
gold  treated  by  percolation,  J  of  a  ton  of  solution  may  dissolve 
the  metals  and  f  of  a  ton  may  wash  them  from  a  ton  of  the  ore. 
Other  ores  in  which  the  metal  is  slowly  dissolved,  as  those  of 
silver,  may  require  many  tons  applied  continuously,  so  that 
dissolution  and  washing  continue  together  until  no  longer 
profitable. 

Time  Required  for  Dissolution.  —  The  time  required  for  dis- 
solving the  gold  and  silver  depends  upon  the  nature  of  the  ore 
and  its  treatment;  the  size  and  thickness  of  the  metal  particles; 
the  mechanically-held,  chemically-combined,  and  metallically- 
alloyed  condition  of  the  metals;  the  action  of  cyanicides  and 
reducers;  the  cyanide  strength  of  solution;  and  the  volume  of 
solution  as  referring  to  keeping  a  solution  that  is  an  active  dis- 
solver  always  in  contact  with  the  ore.  With  some  ores  contain- 
ing extremely  fine  gold  practically  all  the  dissolvable  gold  will 
be  in  solution  by  the  time  the  pulp  leaves  the  tube  mill,  when 
crushing  and  sliming  in  cyanide  solution.  Where  the  metal  is  in 
coarse,  thick  particles,  chemically  combined  or  mechanically 
covered  or  alloyed,  or  only  a  small  part  of  its  area  or  cross- 
section  is  exposed  to  the  cyanide  activity,  the  dissolution  must 
be  comparatively  slow.  The  presence  of  cyanicides  consuming 
the  cyanide  and  oxygen  render  the  dissolution  slow,  owing  to  the 
inability  to  get  these  to  the  dissolving  metal  as  fast  as  needed,  or 
to  their  more  or  less  complete  destruction.  Weak  solutions  are 
more  slowly  solvent  than  strong  ones  in  the  presence  of  sufficient 
oxygen,  consequently: 

Maximum  dissolution  =  Strength  of  solution  X  Dissolution 
period. 

•k 

In  which  either  or  both  of  the  factors,  " strength  of  solution" 
or  "  dissolution  period,"  may  be  varied  within  certain  limits  to 


DISSOLUTION  OF  GOLD  AND  SILVER  19 

produce  a  corresponding  result  in  their  products  —  the  "  maxi- 
mum dissolution  "or  "  rate  of  dissolution."  That  is,  a  strong 
solution  will  dissolve  the  same  amount  of  metal  as  a  weak  one  in 
a  less  length  of  time,  but  a  weaker  solution  given  a  longer  contact 
will  generally  dissolve  the  same  amount  at  a  slower  rate  than  a 
strong  one.  However,  this  rule  is  subject  to  the  chemical  law  of 
mass  action. 

Gold  ores  will  usually  require  a  contact  of  12  hours  to  3  days 
for  dissolution  of  the  gold  by  leaching,  or  3  to  18  hours  by  agita- 
tion. Silver  ores  may  require  a  contact  of  4  to  12  days  by 
leaching,  or  18  hours  to  3  days  by  agitation.  Concentrate  may 
require  a  contact  of  10  to  30  days  by  leaching,  or  12  hours  to  10 
days  by  agitation.  The  fineness  to  which  the  ore  is  ground,  out- 
side of  leaching  vs.  agitation,  is  usually  the  most  important  factor 
in  the  rate  of  dissolution  in  practice  for  reasons  that  have  been 
referred  to. 

Silver  Ores.  —  Silver  ores  require  to  be  treated  with'  stronger 
solutions  and  for  a  greater  length  of  time  than  gold  ores,  for  the 
metal  in  a  gold  ore  is  usually  as  native  gold  or  a  gold-silver  alloy 
in  small  particles,  while  the  silver  in  a  silver  ore  is  more  often  as 
a  compound  with  sulphur,  bromine,  chlorine,  antimony,  arsenic, 
etc.,  usually  the  first.  When  it  occurs  as  native  silver  the  mass 
is  relatively  large  as  compared  with  the  mass  of  the  gold  of  a 
gold  ore,  and  in  all  cases  the  mass  or  amount  of  the  silver  is  com- 
paratively large.  It  has  also  been  shown  that  the  rate  of  solu- 
bility of  silver  is  about  two-thirds  that  of  gold,  while  almost 
double  the  amount  of  cyanide  is  required  in  the  formation  of  the 
silver  potassium  cyanide  as  the  gold  potassium  cyanide. 

The  solution  of  silver  from  the  silver  sulphide  (Ag2S)  —  the 
principal  silver  mineral  worked  by  cyanidation  —  proceeds 
through  the  decomposition  of  the  sulphide  by  cyanide,  as : 

Ag2S  +  4  KCN  =  2  KAg(CN)2  +  K2S. 

In  which  1  part  of  cyanide  dissolves  .414  parts  of  silver,  or  one- 
half  as  much  as  of  native  silver  and  about  one-quarter  as  much  as 
of  native  gold.  Unfortunately  the  soluble  or  alkaline  sulphide 
(K2S)  formed  is  not  stable,  and  in  a  weak  solution  the  silver  sul- 
phide may  not  be  decomposed,  or  if  it  is  the  alkaline  sulphide  may 
tend,  especially  if  the  solution  becomes  weakened,  to  reverse  the 
reaction  by  which  it  was  formed  and  reprecipitate  the  silver  as  a 


20  TEXT  BOOK  OF  CYANIDE  PRACTICE 

sulphide.  Consequently  the  solution  must  be  strong  to  decom- 
pose the  sulphide  and  hold  the  silver  in  a  dissolved  condition. 
The  alkaline  sulphide  if  not  precipitated  as  an  insoluble  sulphide 
by  some  metal  in  solution,  as  lead,  zinc,  or  mercury,  will  unite 
with  the  cyanide  and  with  oxygen  to  form  a  sulphocyanide  or 
thiocyanate,  or  will  be  oxidized  into  a  sulphate,  which  is  one  of 
the  reasons  for  using  a  large  volume  of  freshly-aerated  solution  in 
the  treatment  of  silver  ores.  The  subject  of  alkaline  sulphides  is 
more  fully  treated  under  Alkaline  Sulphides  and  Sulphocyanides. 
The  dissolution  of  silver  from  the  other  ores  must  necessarily 
be  slow  and  consume  much  cyanide  and  oxygen,  owing  to  the 
necessity  of  breaking  down  the  silver  compounds  in  removing 
the  silver  from  them. 


CHAPTER  IV 

SUITABILITY  OF  AN   ORE   FOR  CYANIDATION 

IT  may  be  stated  tentatively  that  all  ores  of  gold  and  most 
silver  ores  can  be  cyanided.  Modifications  and  special  treatment 
may  be  required  with  refractory  ores,  but  those  ores  for  which 
some  successful  treatment  system  cannot  be  devised  are  few. 
The  refractory  qualities  of  an  ore  toward  cyanide  are  of  two 
kinds,  physical  and  chemical.  What  may  be  termed  refractory 
physical  qualities  refer  to  the  necessity  of  crushing  the  ore  ex- 
tremely fine  to  liberate  the  metal  to  the  solvent  action  of  cyanide 
solution,  and  to  the  trouble  encountered  in  treating  a  very  slimy 
material ;  these  will  be  considered  elsewhere.  To  speak  of  an  ore 
as  being  refractory  to  treatment  generally  refers  to  its  chemical 
or  physical-chemical  nature  whereby  the  precious  metals  cannot 
be  economically  dissolved  owing  to  their  being  chemically  com- 
bined or  mechanically  alloyed  with  some  substance  that  prevents 
the  metals  from  being  dissolved  by  cyanide,  also  to  some  con- 
stituent of  the  ore  that  combines  with  the  cyanide  in  large  quan- 
tities or  may  retard  the  dissolution  of  the  precious  metals  from 
the  ore,  or  their  precipitation  from  the  solution.  These  unde- 
sirable constituents  are  spoken  of  as  "  interfering  substances." 
The  results  of  an  analysis  of  an  ore  containing  interfering  sub- 
stances or  refractory  compounds  will  not  indicate  whether  it  can 
be  cyanided  or  not,  for  a  quantity  of  mineral  or  element  which 
may  not  interfere  in  one  ore,  may,  in  a  somewhat  different  form 
in  another,  partly  or  completely  prevent  successful  treatment. 
With  what  success  an  ore  can  be  cyanided  can  only  be  judged 
and  determined  by  laboratory  tests,  preferably  followed  by 
small  working  tests,  which  will  be  discussed  in  a  later  chapter. 

Classification  of  Ores.  —  Ores  may  be  divided  into  three 
classes.  Clean  ores  having  no  sulphides  or  base  metals  and  their 
compounds;  base  ores  containing  unaltered  sulphides  or  base- 
metal  compounds;  and  oxidized  ores  as  a  result  of  the  decom- 
position of  original  base  or  sulphide  ores.  Clean  ores  are  easily 

21 


22  TEXT  BOOK  OF  CYANIDE  PRACTICE 

treated,  as  they  consume  but  little  cyanide,  do  not  introduce 
fouling  substances  into  the  solution,  and  the  precious  metals 
readily  dissolve.  Ores  containing  fresh,  unaltered  sulphides  or 
base  metal  compounds  cyanide  less  easily,  depending  partly 
upon  the  tendency  of  the  sulphides  and  compounds  to  alter  and 
decompose,  thus  consuming  cyanide  and  oxygen,  and  introducing 
substances  that  may  foul  the  solution  toward  further  dissolution 
of  the  gold  and  silver  and  its  precipitation;  also  upon  the  ability 
of  the  cyanide  to  unlock  the  mechanical  or  chemical  combination 
in  which  the  gold  and  silver  is  held  by  the  base  metals.  Oxidized 
ores  act  similarly  to  decomposing  base  ores,  with  the  exception 
that  their  more  complete  decomposition  has  allowed  a  large  part 
of  the  troublesome  constituents  to  be  removed,  though  that 
which  remains  is  in  a  better  condition  to  be  acted  upon  by  cyanide 
and  has  better  liberated  the  precious  metals  for  easy  dissolution. 
Chlorides,  carbonates,  and  partially  oxidized  ores,  as  representing 
an  intermediate  or  final  stage  in  the  transition  of  unaltered  sul- 
phides to  fully  oxidized  or  weathered  ores,  are  the  hardest  to 
treat,  owing  to  the  activity  with  which  cyanide  attacks  these 
soft  and  easily  acted  upon  base  metal  compounds. 

Iron.  —  Metallic  iron  is  so  much  less  soluble  than  gold  and 
silver  in  cyanide  solution  and  dissolves  so  slowly  that  the  fine 
iron  and  steel  introduced  into  the  pulp  in  the  process  of  crush- 
ing and  grinding  has  no  noticeable  deleterious  effects,  but  many 
of  the  iron  compounds  are  readily  acted  upon.  Limonite 
(2  Fe203.3H20),  the  soft,  yellow  iron  oxide,  which  is  found  in 
oxidized  ores  as  one  of  the  final  stages  in  the  oxidation  of  iron,  is 
practically  unacted  upon  by  cyanide  solution,  though  it  causes 
trouble  mechanically  through  its  tendency  to  slime.  Pyrite, 
the  brass-colored,  cubical  iron  sulphide  and  the  one  most  generally 
found,  is  slowly  acted  upon  by  cyanide,  but  does  not  easily  de- 
compose. Marcasite,  the  white  iron  pyrite,  which  is  also  quite 
common,  is  much  less  soluble  in  cyanide  solution  than  pyrite, 
but  readily  decomposes.  Metallic  iron  never  enters  the  solution 
sufficiently  to  be  harmful,  neither  does  metallic  iron  oxidize  to  an 
extent  that  is  injurious  in  ordinary  cases.  It  is  the  products  of 
the  decomposition  of  the  sulphides,  of  which  iron  is  one  of  the 
principal  constituents,  that  are  harmful;  these  are  ferrous  sulphate 
and  oxide,  and  sulphuric  acid,  consuming  the  cyanide  through 
the  iron  entering  the  solution  as  a  potassium  ferrocyanide 


SUITABILITY  OF  AN  ORE  FOR  CYANIDATION    23 

(KiFe(CN)6)  and  the  cyanide  being  neutralized  by  the  acid. 
The  interference  is  met  by  the  use  of  water  washes  removing 
the  soluble  compounds,  and  the  neutralizing  properties  of 
lime  and  alkalinity  as  more  fully  given  under  Alkalinity  and 
Lime. 

Sulphur.  —  Sulphur  does  not  react  directly  with  cyanide,  but, 
as  the  principal  constituent  of  the  sulphides,  it  forms  alkaline 
sulphides  when  the  metallic  sulphides  are  decomposed  by  cyanide 
or  alkali.  The  alkaline  sulphides  react  with  cyanide  and  oxygen 
to  form  sulphocyanides  or  thiocyanates,  or  with  oxygen  to  form 
sulphates,  the  abstracting  of  the  oxygen  being  especially  harm- 
ful. They  also  precipitate  silver  under  certain  conditions  and 
possibly  gold.  The  interference  is  met  by  precipitating  the 
soluble  alkaline  sulphides  by  means  of  zinc,  lead,  or  mercury  into 
inert  sulphides.  The  subject  is  fully  treated  under  Alkaline 
Sulphides  and  Sulphocyanides. 

Copper.  —  Cyanide  has  a  great  affinity  for  copper  and  will 
strongly  act  upon  metallic  copper,  especially  when  finely  divided. 
Copper  compounds  in  a  physically  hard  state,  such  as  unoxidized 
pyrite  or  sulphide,  are  more  slowly  acted  upon.  When  the  com- 
pounds are  soft,  porous,  and  spongy,  the  dissolution  is  fast, 
resulting  in  an  excessive  consumption  of  cyanide,  a  precipitation 
of  copper  in  the  zinc  boxes,  and,  with  much  copper  in  solution, 
trouble  in  dissolving  and  precipitating  the  gold  and  silver. 
Chalcopyrite,  the  principal  copper  sulphide  found  in  gold  ores, 
gives  but  little  trouble  when  unoxidized.  Malachite  and  azurite, 
the  carbonates  of  copper,  are  easily  dissolved  and  a  very  small 
amount  will  give  trouble.  An  assay  of  the  copper  content  of 
the  ore  will  not  indicate  if  it  can  be  profitably  worked,  for  the 
extent  of  the  action  of  cyanide  depends  mainly  upon  the  form  or 
state  the  copper  is  in.  In  some  cases,  as  with  oxides  and  car- 
bonates, a  few  pounds  of  copper  per  ton  of  ore  may  prohibit 
cyaniding  by  ordinary  methods,  whereas  an  ore  containing 
several  per  cent  of  unaltered  chalcopyrite  may  perhaps  be 
amenable  to  treatment.  Modifications  for  treating  copper  ores 
involve  the  use  of  low  strengths  of  solution  and  special  methods 
or  treatment  of  precipitation,  the  use  of  ammonia  as  a  prelimi- 
nary dissolver  of  the  copper  or  to  give  a  greater  selective  action 
to  the  cyanide  solution  on  the  gold,  and  the  preliminary  removal 
of  the  copper  by  concentration  or  a  dilute  acid  wash. 


24  TEXT  BOOK  OF  CYANIDE  PRACTICE 

Lead.  —  Lead  is  strongly  acted  upon  by  cyanide,  but  galena 
(PbS),  the  sulphide  of  lead,  is  only  slightly  attacked  and  very 
slowly  dissolved.  The  cyanidation  of  ores  containing  galena 
is  generally  attended  with  no  excessive  consumption  of  cyanide 
or  any  trouble  except  that  which  but  seldom  occurs  in  the  zinc 
boxes  from  the  precipitation  of  a  large  amount  of  lead.  Finely- 
ground  concentrate  containing  36  per  cent  of  galena  has  been 
successfully  cyanided. 

Arsenic.  —  Arsenic  is  very  slightly  acted  upon  by  cyanide, 
but  may  sometimes  be  found  in  small  quantities  in  the  zinc 
precipitate  resulting  from  the  treatment  of  arsenical  ores.  Mis- 
pickel  or  arsenopyrite  (FeS2.FeAs2),  containing  46  per  cent  of 
arsenic,  a  silver-white  to  steel-gray  pyrite,  is  abundant  in  gold 
ores.  Concentrate  containing  65  to  72  per  cent  of  mispickel  has 
been  successfully  cyanided.  Realgar  (AsS),  the  sulphide  of 
arsenic,  containing  70  per  cent  of  arsenic,  as  a  prominent  con- 
stituent of  ore  has  been  successfully  cyanided,  as  at  Mercur, 
Utah.  Arsenical  ores  in  most  cases  give  a  good  extraction  by 
ordinary  methods,  in  others  they  require  fine-grinding,  the  de- 
composing effect  of  strongly  alkaline  solutions,  roasting,  or  the 
increased  dissolving  effect  of  bromocyanide.  In  some  cases 
the  decomposition  of  the  arsenical  pyrite  or  sulphide  causes  a 
high  consumption  of  cyanide.  In  all  cases  there  is  a  strong 
reducing  action  through  the  formation  of  alkaline  sulphides 
which  must  be  met  by  aerating  the  solution  and  charge,  and  in 
most  cases  by  treatment  for  the  removal  of  the  alkaline  sulphides 
by  other  means.  Arsenical  ores  have  a  reputation  of  being  refrac- 
tory, but  in  most  cases  are  amenable  to  successful  treatment. 

Antimony.  —  Ores  containing  antimony  are  generally  hard 
and  in  some  cases  impossible  to  treat.  Antimony  does  not  appear 
to  react  with  cyanide,  but  the  decomposition  of  stibnite  (Sb2S3), 
the  sulphide  of  antimony,  decomposes  cyanide,  probably  by 
forming  alkaline  sulphides  and  the  resulting  sulphocyanides, 
and  hydrocyanic  acid.  There  is  a  reducing  action  similar  to  that 
with  arsenical  ores,  but  so  pronounced  as  to  make  it  impossible 
to  treat  the  ores  in  some  cases.  With  stibnite  the  precious 
metals  appear  to  be  firmly  held  by  the  antimony  so  that  they 
cannot  be  dissolved  out.  Strongly  alkaline  solutions  will  de- 
compose the  antimony  to  allow  the  precious  metals  to  be  better 
liberated,  but  may  increase  the  reducing  or  deoxidizing  power 


SUITABILITY  OF  AN  ORE  FOR  CYANIDATION     25 

and  cyanide-consuming  tendencies  of  the  ore  to  such  an  extent 
as  to  prohibit  cyanide  treatment.  Preliminary  treatment  with 
hot  alkaline  solutions  has  been  suggested.  Roasting  has  been 
very  successful.  Fine-grinding  will  better  liberate  the  value, 
but  cannot  remove  the  evil  effecfs  on  the  solution. 

Tellurium.  —  Tellurium  does  not  react  with  cyanide  or  only 
slightly  in  alkaline  solutions,  but  holds  the  gold  in  a  chemical 
combination  that  is  unaffected  by  cyanide  under  ordinary  con- 
ditions, so  that  the  usual  processes  give  little  extraction.  Fine- 
grinding  with  the  increased  solvent  action  of  bromocyanide  is 
used  in  Australia  to  extract  the  precious  metals.  The  method 
in  America  has  been  to  break  the  combination  between  the 
precious  metals  and  the  tellurium  by  roasting,  which  volatilizes 
or  oxidizes  the  tellurium,  allowing  the  gold  and  silver  to  be 
readily  dissolved,  but  new  chemical  methods  analogous  to  the 
use  of  bromocyanide  have  been  introduced. 

Mercury  and  Cinnabar.  —  Metallic  mercury  is  so  slowly  dis- 
solved by  cyanide  that  it  introduces  no  difficulties  into  amal- 
gamating in  cyanide  solution,  or  treating  tailing  containing 
metallic  mercury.  The  mercury  in  old  tailing  is  generally 
altered  to  an  oxide  or  chloride  which  is  easily  dissolved  to  be 
precipitated  in  the  zinc  boxes  like  that  dissolved  when  amalga- 
mating in  solution.  The  dissolution  of  a  small  amount  of 
mercury  is  beneficial  in  precipitating  the  obnoxious  soluble 
or  alkaline  sulphides  as  an  insoluble  and  inert  sulphide  of  mercury 
(HgS),  and  in  forming  a  galvanic  couple  with  the  zinc  in  the 
zinc  boxes  which  assists  the  precipitation. 

Cinnabar  (HgS),  the  sulphide  of  mercury,  is  practically  the 
only  mineral  of  mercury  found  in  ores  of  the  precious  metals,  and 
may  be  said  to  be  unaffected  by  cyanide.  In  fact,  mercury  by 
special  treatment  and  gold  by  the  usual  cyanide  treatment  have 
been  produced  from  the  same  ore,  the  production  of  mercury 
ceasing  as  its  percentage  fell,  but  the  cyaniding  for  gold  con- 
tinuing. 

Zinc.  —  Metallic  zinc  is  more  easily  dissolved  than  gold,  but 
sphalerite  or  zinc  blende  (ZnS),  the  sulphide  of  zinc  containing 
67  per  cent  of  zinc,  is  probably  less  acted  upon  by  cyanide  than 
iron  pyrite.  The  products  and  compounds  formed  by  the 
oxidation  or  decomposition  of  zinc  blende,  as  the  carbonate  and 
oxide,  act  similarly  to  other  decomposing  sulphides  and  their 


26  TEXT  BOOK  OF  CYANIDE  PRACTICE 

products  for  whose  metallic  base  cyanogen  has  a  strong  affinity, 
consuming  much  cyanide  and  alkali. 

Nickel  and  Cobalt.  —  Nickel  and  cobalt  have  an  effect  in 
cyanide  treatment  similar  to  that  of  copper. 

Manganese.  —  Cyanide  reacts  with  manganese  and  while  it 
may  increase  the  cyanide  consumption,  it  does  not  appear  to 
harm  the  solution,  being  removed  as  an  insoluble  compound  by 
oxidation  or  the  use  of  lime.  Manganese  in  silver  ores  usually 
prevents  a  good  extraction  by  locking  up  the  silver  in  a  manganese 
compound  so  as  to  prevent  the  solution  from  dissolving  it. 
With  the  silver  in  a  soluble  form  and  the  manganese  separate 
from  and  uncombined  with  the  silver,  there  is  no  difficulty  in 
getting  a  good  extraction  and  no  fouling  of  the  solution.  No 
practical  method  of  unlocking  the  silver  from  the  manganese 
compound  has  yet  been  devised,  but  it  would  appear  that  fine- 
grinding,  roasting,  the  use  of  a  supersolvent  as  bromocyanide, 
or  a  treatment  by  acid  or  alkali  to  decompose  and  break  up 
the  compound  are  the  points  from  which  experiments  should 
be  started.  Treatment  with  a  weak  acid  solution  preliminary 
to  cyaniding  has  given  excellent  results  in  laboratory  experi- 
ments. 

Carbon  and  Carbonaceous  Matter.  —  Vegetable  matter,  char- 
coal, and  other  organic  material  in  an  ore  or  tailing  give  trouble 
both  in  the  dissolution  and  in  the  precipitation,  owing  to  their 
deoxidizing  or  reducing  power,  their  cyanide-consuming  proper- 
ties, their  tendency  to  reprecipitate  the  metals  in  the  ore,  and 
to  a  too  vigorous  evolution  of  hydrogen  in  the  zinc  boxes.  Con- 
siderable alkalinity  and  aeration  should  be  used  when  they 
cannot  be  removed.  Lime  itself  may  be  the  source  of  the  trouble 
when  carrying  carbon  introduced  in  the  lime-burning  process. 
Graphite  gives  trouble  mechanically  by  causing  a  scum  or  froth 
and  chemically  by  reprecipitating  the  metals.  The  remedy 
appears  to  be  roasting,  which  may  not  always  be  successful, 
drying  and  agitating  in  that  condition  with  air,  or  by  sun  drying 
and  weathering. 

Aluminum  and  Magnesium.  —  These  metals  as  sulphates 
resulting  from  the  oxidation  and  decomposition  of  sulphides  may 
interfere  by  uniting  with  the  cyanide  to  form  hydrocyanic  acid, 
as: 

MgS04  +  2  KCN  +  2  H20  =  Mg(OH)2  +  K2S04  +  2  HCN. 


SUITABILITY  OF  AN  ORE  FOR  CYANIDATION     27 

These  metals  may  also  be  dissolved  and  precipitated  in  the  zinc 
boxes.  The  presence  of  sufficient  lime  or  alkalinity  will  remedy 
this,  as: 

MgSO4  +  Ca(OH)2  =  Mg(OH)2  +  CaSO4. 

The  calcium  sulphate  (CaSO4)  and  magnesium  hydrate  (Mg(OH)2) 
are  harmless  and  insoluble. 

Silver.  —  The  amenability  of  silver  ores  to  cyanide  treatment 
varies  with  the  nature  of  the  mineral  or  the  silver  compound. 
Argentite  (As^S),  the  silver  sulphide;  cerargyrite  (AgCl),  the 
silver  chloride;  bromyrite  (AgBr),  the  bromide;  embolite 
(Ag(BrCl)),  the  chlorobromide;  and  native  silver  when  in  a 
fine  state  of  division,  are  readily  acted  upon  and  dissolved  by 
cyanide  and  give  a  good  extraction.  Proustite  (Ag3AsS3),  the 
light-red  ruby  silver;  pyrargyrite  (Ag3SbS3),  the  dark-red  ruby 
silver;  and  stephanite  (Ag5SbS4),  the  brittle  silver,  do  not  so 
readily  respond  to  cyanide  treatment;  these  are  the  arsenical 
and  antimonial  ores  of  silver.  Coarse  native  silver  and  that  in 
galena  (PbS),  the  sulphide  of  lead;  in  tetrahedrite  (Cu8Sb2S7), 
the  gray  copper  sulphide;  and  in  sphalerite  or  zinc  blende  (ZnS), 
the  sulphide  of  zinc,  cannot  be  successfully  treated  by  the  cyanide 
process.  Ores  containing  manganese,  in  which  the  silver  is  locked 
with  the  manganese  in  an  embrace  that  cannot  be  broken  by 
cyanide,  are  not  amenable  to  treatment.  The  treatment  of  re- 
fractory silver  ores  includes  fine-grinding  to  liberate  the  precious 
metals  and  allow  the  mineral  to  be  attacked  and  decomposed  in 
general;  in  the  use  of  a  strong  alkalinity  in  the.  cyanide  solutions 
to  assist  in  decomposing  the  sulphides  and  metallic  compounds; 
and  in  the  use  of  lead  and  mercury  salts  to  precipitate  the  alka- 
line sulphides. 


CHAPTER  V 

CHEMISTRY   OF   CYANIDE  SOLUTIONS 

Classification  of  Cyanide  Tests.  —  The  tests  and  experiments 
made  in  connection  with  a  cyanide  plant  may  be  divided  into 
three  classes: 

(1)  Those  made  daily  by  the  man  on  shift,  which  consist  of 
titrating  the  solution  for  its  strength  in  "  free  cyanide  "  and 
possibly  in  "  total  cyanide/'  and  its  alkaline  strength  in  "  pro- 
tective alkalinity,"  as  a  guide  to  the  amount  of  cyanide  to  be 
added   for   dissolving   purposes,    and    the   amount   of   lime   for 
neutralizing. 

(2)  Those  made  daily  by  the  assayer,  which  consist  of  assays 
of  the  ore  before  and  after  treatment,  and  of  the  solutions  used 
in  treatment,   also  of  the  slag,   matte,   and   bullion  produced. 
These  are  made  for  the  purpose  of  determining  if  the  routine  of 
treatment  is  being  carried  out  with  maximum  efficiency,  and  for 
checking  the  bullion  returns. 

(3)  Those  made  by  or  under  the  direction  of  the  chemist  or 
superintendent  of  the  plant,   which  consist  of  laboratory  ex- 
traction and  sizing  tests  on  the  ore,  and  a  determination  and 
investigation  of  certain  or  most  of  the  constituents  of  the  ore, 
solution,  etc.     These  are-  made  for  the  purpose  of  studying  the 
ore  and  its  treatment  with  a  view  to  increasing  the  extraction, 
decreasing  the  costs,   and  meeting  some  unsolved  problem  or 
any  difficulties  that  may  arise   unusual  to  the   daily  routine. 
The  nature  and  extent  of  these  experiments  will  vary  with  each 
plant  and  operator.     The  education,  training,  and  activity  of 
the  operator  is  the*  principal 'determining  factor,  the  necessity  of 
investigation  usually  coming  second.     Because  a  plant  operates 
smoothly  and  an  ore  treats  easily  is  no  reason  for  not  making  a 
thorough  chemical  and  physical  investigation,  for  it  is  the  facts 
brought  out  by  such  an  investigation,  and  corroborated  from  time 
to  time  by  renewed  and  further  investigation,  that  enable  one 
to  operate  a  plant  successfully  and  quickly  locate  and  remedy 
trouble  when  it  arises. 

28 


CHEMISTRY  OF  CYANIDE  SOLUTIONS  29 

The  analytical  chemistry  of  cyanide  solutions  is  an  exhaustive 
subject,  due  to  the  numerous  and  complex  reactions  that  occur 
and  their  influence  when  working  on  mill  solutions,  which  always 
contain  a  multitude  of  complex  substances.  The  methods  to  be 
given  are  the  standard  and  more  simple  methods  in  general  use 
and  adapted  to  ordinary  mill  practice,  for  further  methods  in- 
volving a  thorough  familiarity  with  analytical  chemistry,  the 
student  is  referred  to  "  Clennell's  Chemistry  of  Cyanide  Solu- 
tions," second  edition,  and  the  articles  listed  in  the  Classified 
Bibliography.  Helpful  information  of  a  less  direct  nature  will  be 
found  in  the  works  on  analysis  by  Sutton,  Fresenius,  and  others, 
also  in  the  chemical  journals. 

A.    FREE  CYANIDE 

The  commonest  and  most  important  test  is  for  the  strength 
of  the  solution  in  cyanide  as  a  guide  to  the  quantity  of  solid 
potassium  or  sodium  cyanide  that  must  be  added  to  the  solution, 
by  the  man  on  shift,  to  bring  it  up  to  the  working  strength  used 
in  the  plant.  This  has  been  called  the  test  for  "  free  cyanide." 
The  result  is  taken  to  indicate  in  terms  of  potassium  cyanide, 
all  the  cyanogen  (CN)  or  cyanide  radical  which  is  present  in  the 
solution  as  potassium  cyanide  (KCN),  sodium  cyanide  (NaCN), 
and  all  the  other  simple  cyanides  of  the  alkalis  and  alkaline 
earth  metals.  The  test  for  free  cyanide  in  both  theory  and 
practice  does  not  give  all  the  cyanide  strength  that  has  a  solvent 
action  on  gold  and  silver  —  not  that  of  the  double  cyanides  — 
but  gives  that  strength  obtained  when  making  up  new  solution, 
or  that  additional  strength  obtained  by  adding  the  solid  cyanide 
tq_a  solution  already  in  use  and  in  good  condition.  , 

Standard  Silver  Nitrate  Test.  —  A  standard  silver  nitrate 
(AgN03)  solution  is  made  by  dissolving  6.5232  grams  pure 
crystallized  silver  nitrate  in  water  and  making  up  with  pure 
water  to  one  liter  (1000  c.c.).  To  test  the  cyanide  solution, 
10  c.c.  is  measured  by  a  pipette  into  a  small  beaker  of  three  or 
four  times  that  capacity.  If  the  cyanide  solution  is  turbid  or 
muddy,  it  should  be  filtered  before  being  measured  out.  To 
the  10  c.c.  in  the  beaker  is  added  as  an  indicator  a  few  drops  of 
a  3  to  5  per  cent  solution  —  3  to  5  grams  of  the  salt  or  substance 
dissolved  in  water  and  made  up  to  100  c.c.  —  of  potassium  iodide 
(KI),  though  the  use  of  an  indicator  is  not  highly  important  and 


.-CO- 

/    (As 


30  TEXT  BOOK  OF  CYANIDE  PRACTICE 

it  is  therefore  often  omitted.  The  standard  silver  nitrate  solution 
is  then  run  from  a  burette  into  the  cyanide  solution  in  the  beaker; 
at  first  very  fast,  and  finally  drop  by  drop,  shaking  the  beaker 
that  the  white  cloud,  formed  as  each  drop  of  the  standard  silver 
nitrate  is  run  in,  may  be  dissolved  until  a  faint,  indistinct  white 
cloudiness  appears;  then  cautiously  adding  the  drops  until 
there  is  a  permanent  opalescence,  slightly  yellowish.  Each  c.c. 
of  the  silver  nitrate  solution  used  on  10  c.c.  of  the  cyanide  solu- 
tion indicates  one  pound  of  potassium  cyanide  or  its  equivalent 
in  a  ton  of  solution.  Thus,  if  2.3  c.c.  of  silver  nitrate  were 
required,  the  solution  contains  the  equivalent  of  2.3  pounds 
potassium  cyanide  per  ton. 

In  titrating  weak  solutions  where  close  results  are  required  in 
connection  with  experimental  work,  as  much  as  50  c.c.  of  the 
|  solution  may  be  used  for  a  tes_tj  Excessively  strong  solutions 
may  be  diluted  with  a  little  water  after  the  portion  for  titration 
has  been  measured  out,  to  prevent  the  formation  of  a  granular 
precipitate  of  single  cyanide,  which  does  not  so  readily  dissolve 
as  the  fine,  white  cloud  of  it  first  formed  and  quickly  dissolved  in 
weak  solutions.  It  is  customary  to  titrate  against  a  black  back- 
ground, holding  the  beaker  on  a  level  with  the  eye  and  looking 
through  a  thick  body  of  the  liquid,  that  the  end  reaction  may  be 
better  observed.  Though  the  exactness  of  the  end  reaction  may 
be  observed  with  pleasing  satisfaction  in  the  case  of  solutions 
newly  made  up  for  test  purposes,  the  exact  end  point  cannot  be 
so  easily  distinguished  with  complex  mill  solutions.  The  errors 
that  may  occur  in  this  way  in  the  daily  routine  of  plant  work  or 
through  the  limitations  of  the  method  are  generally  unimpor- 
tant, for  mill  solutions  should  be  of  such  a  strength  that  an 
accidental  reduction  of  10  to  20  per  cent  in  their  working  strength 
for  a  short  period  should  not  be  harmful.  As  the  strength  of 
solution  used  in  a  plant  is  eventually  determined  by  the  results 
obtained  in  practice  and  various  experiments  relating  to  the 
daily  practice,  the  careful  operator  instructs  his  shift  men  to 
carry  the  end  reaction  to  the  same  point  that  he  does,  thereby 
keeping  the  error  —  usually  a  case  of  carrying  the  reaction  too 
far  and  overestimating  the  strength  —  constant  and  minimizing 
the  danger  in  this  direction. 

p     Reactions  in  Standard  Silver  Nitrate  Test.  —  The  test  depends/ 

/  upon  the  following  reactions: 


CHEMISTRY  OF  CYANIDE  SOLUTIONS  31 

A.  AgNO3+  KCN  =  AgCN  +  KNO3, 

B.  AgCN  +  KCN  =  KAg(CN),, 

C.  AgNO3+  KAg(CN)2  =  2  AgCN  +  KN03, 

in  which  the  single  silver  cyanide  (AgCN)  formed  in  A}  as  indi- 
cated by  the  temporary  white  precipitate  or  cloud,  redissolves 
in  an  excess  of  cyanide  to  form  the  soluble  double  silver  cyanide 
(KAg(CN)2)  in  B.  After  all  the  cyanide  has  been  converted 
into  the  double  silver  cyanide,  an  additional  drop  of  the  silver 
nitrate  will  cause  a  precipitate  of  the  single  silver  cyanide  as  in 
C,  which  is  insoluble  and  does  not  dissolve  in  the  absence  of  free 
cyanide,  but  forms  a  permanent-Dpalescence--- 

The  amount  of  silver  nitrate  to  be  used  in  standardizing  may 
be  computed  by  combining  A  and  B  into  one  equation,  since  the 
silver  nitrate  converts  the  cyanide  into  the  double  silver  cyanide, 
as: 

Ag     N     03      +  2       K     C     N  =  KAg(CN)2  +  KN03. 

5  8          E? 
oo    H-       j  (.3          S) 

169.89  130.22 

If  169.89  parts  AgNO3  combine  with  130.22  parts  KCN,  then 

1  on  oo 

1  part  AgNO3  =  y        \  or  .766496  parts  KCN.     If  1000  c.c. 


solution  contains  6.5232  grams  AgNO3,  1  c.c.  will  contain 
.0065232  grams,  which  is  equal  to  .766496  X  .0065232  or  .005 
grams  KCN.  Consequently  if  1  c.c.  of  AgNO3  solution  is  re- 
quired on  10  c.c.  of  the  cyanide  solution,  the  10  c.c.  contains  .005 
grams  KCN,  equal  to  .05  per  cent  or  1  pound  KCN  per  ton 
solution. 

Reactions  of  the  Potassium  Iodide.  —  The  use  of  a  few  drops 
of  a  neutral  3  to  5  per  cent  solution  of  potassium  iodide  (KI)  is 
said  to  correct  or  reduce  the  liability  of  errors  in  titrating  com- 
plex mill  solutions,  but  is  added  mainly  as  an  "indicator"  to 
make  the  end  reaction  more  distinct.  The  reactions  occurring 
are  somewhat  similar  to  those  in  the  case  of  cyanide: 

A.  AgNO3  +  KI  =  Agl  +  KN03, 

B.  Agl  +  2  KCN  =  KI  +  KAg(CN)2, 

C.  AgNO,  +  KI  =  Agl  +  KN03, 

in  which  any  single  silver  iodide  (Agl)  as  first  formed  in  A  is 


32  TEXT  BOOK  OF  CYANIDE  PRACTICE 

dissolved  by  an  excess  of  cyanide  to  form  the  double  silver 
cyanide,  while  the  iodide  again  becomes  potassium  iodide,  as  in 
B.  When  no  more  free  cyanide  is  present,  the  single  silver 
iodide  forms  and  remains  as  a  permanent  precipitate  as  in  C, 
giving  a  yellowish  color  to  the  solution.  The  tendency  is  for  the 
iodide  in  a  cyanide  solution  to  be  precipitated  in  preference  to 
the  cyanide,  consequently  the  final  permanent  precipitate  where 
the  potassium  iodide  indicator  is  used  becomes  more  the  final 
potassium  iodide  reaction  of: 

C.   AgN03  +  KI  =  Agl  +  KN03, 
than  the  final  cyanide  reaction  of: 

C.   AgNO3  +  KAg(CN)2  =  2  AgCN  +  KN03. 

Testing  Strength  of  Solid  Cyanide.  —  The  strength  of  solid 
cyanide  may  be  tested  or  determined  by  this  method  through 
weighing  out  a  sample  of  the  salt  —  from  the  interior  of  the 
cakes  where  the  surface  has  absorbed  moisture  through  exposure 
to  the  atmosphere  —  and  making  it  into  a  solution  of  a  certain 
theoretical  strength,  and  then  titrating  a  sample  of  the  solution. 
Thus  5  grams  of  cyanide  may  be  dissolved  in  water  and  made  up 
to  500  c.c.,  making  a  1  per  cent  (20  pounds)  solution.  Should 
the  solution  titrate  .97  per  cent  (19.4  pounds  per  ton  of  solution) 
strong,  then  it  is  "  97  per  cent  pure  "  or  "  strong  "  potassium 
cyanide.  Should  sodium  cyanide  be  taken,  it  may  be  found  to 
indicate  1.2  per  cent  (24  pounds  per  ton  of  solution),  showing  that 
the  cyanide  is  120  per  cent  strong  when  computed  in  terms  of 
potassium  cyanide. 

B.    HYDROCYANIC   ACID   AND   ACIDITY 

Occurrence.  —  The  hydrocyanic  acid  existing  in  cyanide  solu- 
tion is  formed  mainly  by  the  decomposition  of  cyanide  by  acids 
in  the  ore,  as: 

H2S04  +  2  KCN  =  2  HCN  +  K2SO4. 

Test  for  Hydrocyanic  Acid.  —  The  hydrocyanic  acid  may  be 
determined  in  cyanide  solutions  by  first  estimating  the  free 
cyanide  in  the  usual  way.  Another  sample  of  the  solution  is 
then  taken,  to  which  is  added  an  excess  of  a  solution  of  potassium 
or  sodium  bicarbonate  (KHC03  or  NaHC03).  The  solution  is 
then  titrated  with  the  standard  silver  nitrate  solution  without 


CHEMISTRY  OF  CYANIDE  SOLUTIONS  33 

the  indicator,  and  the  difference  between  this  titration  and  that 
for  free  cyanide  is  taken  as  the  hydrocyanic  acid. 

The  addition  of  the  solution  of  potassium  or  sodium  bicar- 
bonate causes  the  following  reaction: 

HCN  +  KHCO3  =  KCN  +  C02  +  H20. 

Since  the  HCN  is  titrated  as  KCN  and  the  atomic  weight  of 
hydrogen  (H)  is  1,  of  potassium  (K)  is  39.1,  of  carbon  (C)  is  12, 
and  of  nitrogen  (N)  is  14: 


1      12     14 

H     C      N       27 


KCN      65.1 
39.1    12     14 


=  .415. 


The  above  titration  less  that  for  free  cyanide  indicates  directly 
the  pounds  of  potassium  cyanide  to  which  the  cyanogen  of  the 
hydrocyanic  acid  is  equivalent,  or  when  multiplied  by  .415  the 
result  indicates  the  amount  of  hydrocyanic  acid. 

Acidity  Test  for  Hydrocyanic  Acid.  —  Another  method  of  de- 
termining the  hydrocyanic  acid,  one  which  may  more  properly 
be  denned  as  giving  the  "  acidity  "  of  the  cyanide  solution  in  the 
absence  of  any  protective  alkalinity,  consists  in  neutralizing  the 
cyanide,  rendering  the  zinc  innocuous,  and  determining  the 
acidity  with  standard  alkali.  For  this  test  one-half  more  to 
double  the  amount  of  standard  silver  nitrate  required  in  the 
total  cyanide  test  is  added  to  10  c.c.  of  the  cyanide  solution,  to 
convert  all  the  free  cyanide  and  any  other  easily-decomposed 
cyanides  into  the  double  silver  cyanide  salt  neutral  to  acidity  or 
alkalinity.  To  this  is  added  about  5  c.c.  of  a  5  per  cent  solution 
of  potassium  ferrocyanide  (K4Fe(CN)6)  or  an  excess  over  that 
required  to  precipitate  the  zinc  in  the  solution  as  a  potassium 
zinc  ferrocyanide  (K2Zn(Fe(CN)6))  inert  in  the  test.  Phenol- 
thalein  is  now  added  as  an  indicator  of  alkalinity  and  if  the  solu- 
tion turns  red,  indicating  that  there  is  a  protective  alkalinity,  it 
should  be  titrated  with  the  standard  decinormal  acid  solution 
for  the  amount  of  protective  alkalinity.  But  if  the  solution  does 
not  turn  red,  it  is  either  neutral  or  acid  and  should  be  titrated 
with  standard  decinormal  alkali  until  the  solution  becomes 
alkaline  by  turning  red,  for  the  amount  of  acidity.  (See  Pro- 
tective Alkalinity  for  the  preparation  and  use  of  standard  acid 
and  alkali  solutions  and  indicators.)  The  acidity  may  be  re- 


34  TEXT  BOOK  OF  CYANIDE  PRACTICE 

ported  in  the  number  of  pounds  of  caustic  soda  (NaOH).  or  lime 
(CaO)  that  would  be  required  per  ton  of  solution  to  neutralize 
the  acidity,  the  number  of  pounds  of  hydrocyanic  acid  it  repre- 
sents, or  the  cyanide  that  has  been  decomposed.  Using  10  c.c. 
of  cyanide  solution,  each  c.c.  of  the  standard  decinormal  alkali 
equals  .04  per  cent  (.8  pound  per  ton  of  solution)  caustic  soda 
(NaOH)  or  .028  per  cent  (.56  pound)  lime  (CaO).  Or  each 
cubic  centimeter  of  the  decinormal  alkali  used  equals  .027  per 
cent  (.54  pound)  hydrocyanic  acid  (HCN),  as  indicated  by  the 
equation: 

(1  +  12  +  14)  +  (23  +  16  +  1)  =  (23  +  12  +  14)  +((2  X  1)  +  16) 

H      C       N   +  Na       0      H  =  Na      C        N  +          H2       O. 

27  40  49  18 

A  decinormal  caustic  soda  solution  contains  4  grams  NaOH  in 
1000  c.c.,  or  .004  grams  NaOH  in  each  c.c.  In  the  equation  40 
parts  NaOH  neutralizes  27  parts  HCN,  or  1  part  NaOH  equals 
.675  parts  HCN,  therefore  1  c.c.  decinormal  alkali  equals  .675 
X  .004  grams  or  .0027  grams  HCN.  If  1  c.c.  decinormal  alkali 
is  equal  to  .0027  grams  HCN  in  10  c.c.  of  cyanide  solution,  it  is 
equivalent  to  .027  per  cent  HCN  or  .54  pound  per  ton.  Since, 
as  shown  before,  the  cyanogen  in  .415  pound  HCN  is  equiva- 
lent to  that  in  1  pound  KCN,  .027  per  cent  or  .54  pound  HCN 
equals  .065  per  cent  or  1.3  pounds  KCN  per  ton  solution.  To 
tabulate: 
One  c.c.  decinormal  alkali  taken  in  10  c.c.  solution 

=  .04    per  cent  NaOH  or  .8  pound  per  ton  solution. 

=  .028  per  cent  CaO  or  .56  pound  per  ton  solution. 

=  .027  per  cent  HCN  or  .54  pound  per  ton  solution. 

=  .065  per  cent  KCN  or  1.3  pounds  per  ton  solution. 

Nature  of  Acid  Cyanide  Solutions.  —  Cyanide  solutions  do 
not  often  become  acid  with  careful  manipulation,  operators 
universally  aiming  to  have  at  least  a  slight  protective  alkalinity. 
Though  in  working  gold  ores  a  few  cases  have  been  reported 
where  a  slight  acidity  of  the  solutions  seemed  beneficial,  appar- 
ently owing  to  the  retarding  influence  of  excessive  alkalinity  on 
the  dissolution  of  gold  and  the  deleterious  effects  of  the  substances 
resulting  from  the  decomposition  of  sulphides  and  base  com- 
pounds by  alkali,  mainly  the  alkaline  sulphides  produced, 
generally  a  solution  that  is  acid  causes  a  waste  of  cyanide  by 


CHEMISTRY  OF  CYANIDE  SOLUTIONS  35 

the  new  acid  that  appears,  a  poor  extraction  through  the  fouling 
of  the  solution  by  base  metals  which  alkali  would  render  inert, 
and  a  poor  precipitation  in  the  zinc  boxes,  especially  with  a 
weak  solution,  when  the  tendency  for  a  white  precipitate  of  zinc 
cyanide  to  be  formed  in  the  boxes  is  great,  owing  to  the  inability 
of  the  weak  solution  to  hold  the  zinc  cyanide  in  a  dissolved  or 
soluble  state.  ' 

C.   TOTAL  CYANIDE 

Definition.  —  The  test  for  total  cyanide  is  considered  to  give, 
in  terms  of  potassium  cyanide,  all  of  the  cyanogen  or  CN  radical 
present  in  the  form  of  simple  cyanides  as  determined  by  the  test 
for  free  cyanide,  which  is  the  potassium  and  sodium  cyanide  and 
the  other  single  cyanides  of  the  alkalis  and  alkaline  earths  metals, 
and  additionally  that  contained  in  the  hydrocyanic  acid  (HCN) 
and  the  double  cyanide  of  zinc  (K2Zn(CN)4)  and  possibly  some 
other  easily-decomposed  double  cyanides. 

Test  with  Standard  Silver  Nitrate  and  Alkali.  —  For  deter- 
mining the  total  cyanide,  from  10  to  50  c.c.  of  the  cyanide  solu- 
tion to  be  tested  are  taken,  a  few  drops  of  the  potassium  iodide 
indicator  are  added,  and  then  a  few  cubic  centimeters  of  a  nor- 
mal caustic '  soda  (XaOH)  or  caustic  potash  (KOH)  solution  — 
sufficient  to  make  the  solution  excessively  alkaline.  It  is  then 
titrated  with  the  standard  silver  nitrate  solution  as  in  the  case 
of  free  cyanide,  carrying  the  titration  past  a  white  turbidity 
until  a  permanent  yellow  color  is  obtained.  The  number  of 
cubic  centimeters  of  silver  nitrate  solution  used  in  10  c.c.  of 
cyanide  solution  indicates  in  terms  of  potassium  cyanide  the 
number  of  pounds  of  total  cj-anide  in  a  ton  of  solution.  It 
should  be  observed  if  increasing  the  amount  of  alkali  added  will 
increase  the  total  cyanide  obtained,  the  highest '  result  being 
taken. 

The  normal  caustic  alkali  solution  is  made  by  dissolving  4 
grams  caustic  soda  or  5.6  grams  caustic  potash  in  water  and 
making  up  to  100  c.c.  Any  strength  of  caustic  alkali  solution 
may  be  used  in  a  sufficient  quantity. 

Reactions  in  Total  Cyanide  Test.  —  The  above  test  depends 
in  the  case  of  hydrocyanic  acid  upon  the  production  of  a  cyanide 
on  the  addition  of  an  alkali  to  hydrocj'anic  acid,  as: 
HCN  +  KOH  =  KCN  +  H,O. 


36 


TEXT  BOOK  OF  CYANIDE  PRACTICE 


In  the  case  of  the  zinc  potassium  cyanide  (K2Zn(CN)4)  and 
other  easily-decomposed  double  cyanides,  the  addition  of  an 
alkali  causes,  or  apparently  causes,  a  formation  or  regeneration 
into  the  simple  cyanide,  as: 

K2Zn(CN)4  +  4  KOH  =  4  KCN  +  Zn(KO)2  +  2  H2O. 

Action  of  Double  Cyanides.  —  This  is  an  important  test,  but 
in  most  cases  is  only  made  occasionally  by  the  chemist  in  charge. 
The  importance  of  the  test  arises  from  the  fact  that  it  has  been 
found  both  in  laboratory  experiments  and  plant  practice,  that 
zinc  potassium  cyanide  is  an  active  solvent  of  gold  and  silver, 
and  more  active  when  apparently  regenerated  into  KCN  or  a 
simple  cyanide  by  the  addition  of  alkaH,  as  shown  in  the  last 
equation.  The  following  from  tests  by  W.  H.  Virgoe*  is  typical: 


Test  No. 

Solvent. 

Strength. 

KCN 

Consumption. 

Extraction. 

Per  cent 

Lbs. 

Per  cent 

1 

KCN 

.22 

1.0 

87 

2 

K,Zn(CN)4 

.22 

0.4 

45 

3 

K2Zn(CN)4+CaO 

.22 

0.2 

75 

The  practice  that  the  above  test  would  indicate  has  been 
adopted  in  many  silver  plants  by  adding  the  lime  used  for 
neutralizing  and  for  giving  a  protective  alkalinity  in  such  a 
quantity  that  the  tests  for  free  and  total  cyanide  closely  approach 
each  other  or  are  practically  the  same,  thus  performing  in  the 
plant  practice  what  is  experimentally  performed  in  the  total 
cyanide  test.  The  following  adapted  data  by  L.  N.  B.  Bullock 
regarding  his  cyanide  practice  at  Copala,  Sonora,  Mexico,!  is  an 
excellent  illustration  of  this  principle  put  into  practice.  The 
ore  is  valuable  for  its  silver,  which  occurs  as  a  sulphide  and 
carries  from  12  to  20  ounces  of  the  metal  per  ton.  When  treat- 
ment was  first  commenced  the  protective  alkalinity  in  the  work- 
ing solution  was  carried  at  .04  per  cent  NaOH  (.56  pound  lime 
(CaO)  per  ton  solution),  the  use  of  5.2  pounds  lime  per  ton  of 
ore  being  sufficient.  The  cyanide  consumption  varied  from  4.3 
to  4.5  pounds  per  ton  of  ore.  With  the  object  of  ascertaining 
what  results  could  be  secured  by  decomposing  the  zinc  cyanide 

*  Journal  Chemical,  Mining,  and  Metallurgical  Soc.  of  S.  A.,  Vol.  4,  Aug., 
1903. 

t  Mining  and  Scientific  Press,  June  8,  1907.  Recent  Cyanide  Practice, 
pp.  264.- 


CHEMISTRY  OF  CYANIDE  SOLUTIONS          37 

or  double  cyanides  and  regenerating  cyanide  through  increasing 
the  alkalinity,  the  amount  of  lime  used  was  increased  and  kept 
gradually  increasing  until  the  solutions  tested  .2  per  cent  NaOH 
(2.8  pounds  lime  per  ton)  in  protective  alkalinity.  The  working 
solution  for  slime  treatment,  which  was  carried  at  .125  per  cent 
(2.5  pounds)  KCN,  at  once  began  to  gain  in  strength,  and  kept 
gradually  growing  stronger  until  it  showed  .3  per  cent  (6  pounds) 
KCN;  the  alkalinity  then  being  allowed  to  fall  to  .09  per  cent 
NaOH  (1.26  pounds  lime  per  ton),  the  cyanide  strength  also  fell. 
After  many  experiments  with  various  strengths,  it  was  found 
that  .135  per  cent  NaOH  (1.9  pounds  lime  per  ton)  was  the 
least  protective  alkalinity  that  would  give  the  desired  regenera- 
tion of  cyanide,  and  consequently  the  protective  alkalinity  has 
been  kept  at  that  figure  since.  As  a  result  of  this  regeneration 
the  cyanide  consumption  has  not  exceeded  1.5  pounds  per  ton 
treated  for  more  than  five  months  with  no  indication  of  any 
increase;  as  a  matter  of  fact,  no  cyanide  was  added  to  the  slime 
treatment  solutions  for  nearly  13  weeks,  and  the  amount  used 
to  bring  the  leaching  plant  solutions  up  to  strength  was  small; 
this,  of  course,  was  due  to  the  large  excess  of  zinc  cyanide  existing 
in  the  system. 

The  use  of  an  excessive  protective  alkalinity,  while  in  many 
cases  effecting  a  considerable  saving  in  cyanide  and  by  decom- 
posing the  base  metal  compounds  to  some  extent  better  liberates 
the  precious  metals,  decreases  the  solubility  of  native  gold  and 
silver,  lessening  the  extraction  or  increasing  the  time  required  for 
dissolution.  Consequently  an  excessive  alkalinity  is  not  used  in 
treating  gold  ores  and  only  on  silver  ores  when  found  beneficial. 

The  amount  of  double  cyanides  in  a  plant  solution  should  be 
watched  and  an  attempt  made  to  gauge  their  dissolving  influence. 
Where  there  is  a  considerable  amount,  it  is  well  to  report  the 
strength  of  the  solution  in  both  free  and  total  cyanide.  A 
sudden  material  reduction  in  the  amount  of  double  cyanide  may 
indicate  the  need  of  a  solution  stronger  in  free  cyanide,  and  that 
some  important  change  is  taking  place  in  the  solution  that 
should  be  investigated.  The  zinc  potassium  cyanide  is  formed 
by  the  passage  of  the  solution  through  the  zinc  boxes  and  in 
connection  with  the  precipitation.  It  is  customary  to  consider 
the  double  cyanide  or  the  difference  between  the  free  and  total 
cyanide  as  zinc  potassium  cyanide  only. 


38  TEXT  BOOK  OF  CYANIDE  PRACTICE 

D.   PROTECTIVE  ALKALINITY 

Definition.  — •  The  "  protective  alkali  "  of  a  cyanide  solution 
is  taken  to  mean  those  substances,  excepting  the  simple  cyanides 
and  the  easily-decomposed  double  cyanides  determined  by  the 
total  cyanide  test,  that  are  alkaline  to  an  indicator,  the  theory 
being  that  this  protective  alkalinity  will  be  neutralized  or  de- 
stroyed by  any  acidity  which  the  solution  may  encounter,  before 
the  cyanide  is  consumed  or  destroyed;  that  hydrocyanic  acid  will 
be  prevented  from  forming  or  that  which  is  already  formed 
will  be  regenerated  into  free  cyanide;  and  that  many  cyanicides 
will  be  rendered  inert  and  harmless  by  direct  or  indirect  reaction 
with  the  alkali. 

Test  for  Protective  Alkalinity.  —  The  protective  alkalinity  is 
determined  by  taking  10  c.c.  of  the  solution  to  be  tested.  To 
this  is  added  about  5  c.c.  or  sufficient  of  a  5  per  cent  solution  of 
potassium  ferrocyanide  (K4Fe(CN)6)  that  any  zinc  in.  solution 
as  the  double  cyanide  or  otherwise  may  be  rendered  neutral  by 
conversion  into  zinc  potassium  ferrocyanide,  as: 

K4Fe(CN)6  +  K2Zn(CN)4  =  K2ZnFe(CN)6  +  4  KCN. 

The  cyanide  liberated  in  this  equation  is  converted  by  an 
excess  of  silver  nitrate  into  a  double  silver  cyanide,  which,  like 
the  zinc  potassium  ferrocyanide,  is  neutral  and  inert  to  indicators 
in  the  test.  Standard  silver  nitrate  is  added  for  this  purpose 
to  the  extent  of  perhaps  one-half  more  or.  double  that  required 
in  the  determination  of  total  cyanide,  to  insure  all  the  cyanide 
being  converted  into  the  neutral  double  silver  cyanide.  A  few 
drops  of  phenolthalein  solution  are  then  added,  which  will  turn  the 
solution  a  bright  red  if  any  protective  alkalinity  is  present.  The 
solution  will  be  unchanged  if  it  is  neutral  or  acid,  in  which  case 
it  should  be  titrated  for  its  "  acidity  "  with  decinormal  alkali 
as  described  in  the  test  for  hydrocyanic  acid.  If  the  solution  is 
alkaline,  it  is  titrated  with  decinormal  acid  until  the  red  or  pink 
shade  of  phenolthalein  just  disappears.  Each  cubic  centimeter 
of  the  decinormal  acid  used  on  10  c.c.  of  solution  indicates  the 
following  equivalents: 

.04  per  cent  caustic  soda  (NaOH),  or  .8  pound  per  ton  solution. 
.056  per  cent  caustic  potash  (KOH),  or  1.12  pounds  per  ton 
solution. 


CHEMISTRY  OF  CYANIDE  SOLUTIONS          39 

.028  per  cent  unslacked  lime  (CaO),  or  .56  pound  per  ton  solution. 

.037  per  cent  slacked  lime  (Ca(OH)2),  or  .74  pound  per  ton  so- 
lution. 

In  mill  work  the  results  should  be  reported  in  pounds  of  the 
neutralizer  used  —  invariably  unslacked  lime  (CaO)  —  per  ton 
of  solution.  Percentage  may  be  used  for  technical  purposes, 
and  the  kind  of  alkali  in  terms  of  which  the  results  are  stated, 
preferably  as  NaOH  or  CaO,  should  always  be  given.  The  test 
may  be  conveniently,  though  somewhat  less  accurately,  made  in 
mill  work  by  adding  the  silver  nitrate  in  excess  after  the  usual 
free  cyanide  test,  then  with  or  without  potassium  ferrocyanide, 
adding  the  indicator  and  titrating. 

Preparation  of  Indicators.  —  The  phenolthalein  solution  is 
prepared  by  dissolving  5  grams  of  phenolthalein  in  1  liter 
(1000  c.c.)  of  a  solution  one-half  pure  water  and  one-half  alcohol. 
Methyl  orange  may  also  be  used  as  an  indicator,  except  with 
oxalic  acid.  It  is  prepared  by  dissolving  1  gram  of  the  powder 
in  1  liter  of  water.  Litmus  is  seldom  used. 

Theory  of  Standard  Acid  and  Alkali  Solutions.  —  A  normal 
(N)  solution  of  a  substance  contains  in  1  liter  of  the  solution, 
the  molecular  weight  in  grams  of  the  substance  divided  by  the 
number  of  atoms  of  the  active  element  (hydrogen  or  hydrogen 
equivalent)  in  the  molecule  of  the  substance.  One  c.c.  of  such 
a  solution  prepared  from  any  acid  will  be  exactly  neutralized  by 
1  c.c.  of  such  a  solution  of  any  alkali,  by  the  active  base  of  the 
alkali  replacing  the  hydrogen  equivalent  of  the  acid,  as: 

JHC1  +  NaOH  =  NaCl  +  H2O. 
lH2S04  +  2  NaOH  =  Na2S04  +  2  H20. 

CN\  /N\  /N\ 

2-J,  fifth-normal (—  1,  or  decinormal  (— J  solution 

is  one-half,  one-fifth,  or  one-tenth  as  strong  as  a  normal  (N) 
solution. 

Preparation  of  Standard  Decinormal  Acid  and  Alkali  Solu- 
tions. —  The  standard  acid  solution  may  be  prepared  from  nitric 
acid  (HNO3),  hydrochloric  acid  (HC1),  sulphuric  acid  (H2SO4), 
or  oxalic  acid  (C2H2O4.2  H20),  usually  from  the  latter  two.  A 


decinormal  1^1  acid  solution  made  up  to  1000  c.c.  with  pure 
water  contains  4.9  grams  H2S04,  3.646  grams  HC1,  6.3  grams 


40  TEXT  BOOK  OF  CYANIDE  PRACTICE 

HNO3,  or  6.3  grams  C2H2O4.2H2O.  The  quantities  being 
arrived  at  by  dividing  the  molecular  weight  of  the  acid  by  the 
number  of  hydrogen  atoms  in  the  chemical  proper  (not  including 
the  water  of  crystallization),  and  again  by  10  to  give  the  amount 
for  a  decinormal  solution,  as: 

H2      S      O4 
2  +  32  +  64  =  98  -=-  2  -^  10  =  4.9. 

H      Cl 
1  +  35.46  =  36.46  -^  1  -H  10  =  3.646. 

H      N      03 
1  +  14  +  48 _  =  63  ^  1  -^  10  =  6.3. 

C2     H2     O4.      2H20 

24  +  2  +  64  +  4  +  32  =  126  -s-  2  ^  10  =  6.3. 

For  mill  work  the  solution  may  be  prepared  by  weighing  out, 
or  by  measuring  from  a  burette,  the  required  amount  of  the 
highest-grade,  chemically-pure  acid  of  a  reputable  maker,  and 
diluting  with  pure  water  up  to  the  necessary  amount.  When 
the  acid  is  measured  from  a  burette  the  amount  must  be  calcu- 
lated from  its  specific  gravity,  for  as  water  has  been  given  a 
specific  gravity  of  one  as  a  standard  and  1  c.c.  has  been  taken  as 
weighing  1  standard  gram,  so  does  a  cubic  centimeter  of  sul- 
phuric acid  of  1.845  specific  gravity  weigh  1.845  grams,  and 
similarly  with  the  other  acids.  For  more  exact  work  the  acid 
solution  must  be  standardized  against  a  standard  alkali  solution 
of  high  accuracy,  though  solutions  prepared  from  oxalic  acid  are 
very  accurate  without  standardizing.  Pure  sodium  carbonate 
(Na2C03)  is  heated  without  fusing,  to  drive  off  the  absorbed 
moisture,  in  a  porcelain  or  platinum  dish  until  the  dish  assumes 
a  dull-red  color,  being  kept  at  that  heat  for  about  15  minutes. 
It  is  cooled  under  a  dessicator  and  5.3  grams  (Na2C03  =  2(23) 
+  12  +  3(16)  =  106  +  2  -T-  10  =  5.3)  weighed  out  quickly,  - 
to  prevent  absorption  of  moisture,  —  dissolved  in  water,  and 
made  up  to  1000  c.c.  This  is  an  exact  decinormal  alkali  solution 
of  which  25  or  50  c.c.  are  taken,  the  indicator  added,  and  titra- 
tion  made  with  the  decinormal  acid  solution,  which  must  \^ 
diluted  with  water  Q^  strengthened  with  acid  until  a  cubic  centi- 
meter of  the  standard  acid  will  exactly  neutralize  a  cubic  centi- 
meter of  the  standard  alkali. 


.      CHEMISTRY  OF  CYANIDE  SOLUTIONS  41 

Decinormal  alkali  for  rough  mill  work  is  prepared  by  dis- 
solving 4^rams  of  caustic  soda  (NaOH  =23  +  16  +  1  =40 
-T-  1  -r-  10  =  4),  or  5.61  grams  caustic  potash  (KOH  =  39.1 
+  16  +  1  =  58.1  -f-  1  -f-  10  =  5.61)  and  making  up  to  1000  c.c. 
with  water.  The  pure  chemical  should  be  used  from  a  well- 
stoppered  bottle  in  which  the  tendency  to  deliquesce  or  absorb 
moisture,  which  is  especially  great  with  caustic  potash,  is  at  a 
minimum.  The  solution  in  any  case  will  not  be  very  accurate 
and  should  be  adjusted  to  a  standard  acid  solution. 

When  using  10  c.c.  of  the  cyanide  solution,  each  cubic  centi- 
meter of  the  decinormal  acid  used  indicates  a  protective  alka- 
linity, or  each  cubic  centimeter  of  the  decinormal  alkali  used 
equals  an  acidity  equal  to  the  following: 

.04    per  cent  caustic  soda  (NaOH) ,  or  .8  pound  per  ton  solution. 

.056  per  cent  caustic  potash  (KOH),  or  1.12  pounds  per  ton  solu- 
tion. 

.028  per  cent  unslacked  lime  (CaO),  or  .56  pound  per  ton  solu- 
tion. 

.037  per  cent  slacked  lime  (Ca(OH)2),  or  .74  pound  per  ton  solu- 
tion. 

The  above  values  may  be  computed  from  the  quantities  in  any 
of  the  standard  acids  or  alkalis,  since  they  exactly  equal  or 
neutralize  each  other.  Taking  caustic  soda  as  the  illustration, 
the  decinormal  solution  contains  4  grams  in  1000  c.c.,  or  .004 
gram  in  each  cubic  centimeter.  The  .004  gram  NaOH  or  its 
equivalent  in  acid  used  in  titrating  10  c.c.  of  solution  is  equal  to 
.04  per  cent  of  the  10  c.c.,  showing  the  solution  to  contain  the 
equivalent  of  .04  per  cent  NaOH.  The  value  of  the  caustic 
potash  can  be  figured  out  in  a  similar  way,  using  5.61  grams  as 
required  in  the  decinormal  solution.  In  the  case  of  unslacked 
lime  (CaO),  one  atom  of  calcium  (Ca)  replaces  two  of  hydrogen 
as  indicated  in  the  formation  of  calcium  sulphate  by  sulphuric 
acid  and  lime : 

H2SO4  +  Ca  =  CaSO4  +  2  H. 

Consequently  CaO  =  40  +  16  =  56  -T-  2  +  10  =  2.8  grams  in 
1000  c.c.  of  decinormal  solution  or  .0028  gram  in  each  cubic 
centimeter.  The  .0028  gram  or  its  equivalent  in  acid  used  in 
titrating  10  c.c.  of  solution  is  equal  to  .028  per  cent  of  the  10  c.c., 
showing  the  solution  to  contain  the  equivalent  of  .028  per  cent 


42  TEXT  BOOK  OF  CYANIDE  PRACTICE     . 

CaO.     The  value  of  slacked  lime  (Ca(OH)2)  may  be  figured  in  a 
similar  way:  Ca(OH)2  =  40+2  (16+ 1)  =  74  •*•  2  -MO  =  3.7  grams 

N 
required  in  1000  c.c.  ^  solution,  and  so  on. 

The  amounts  of  the  chemicals  required  in  1000  c.c.  of  solution 

N 
to  make  up  a  ^  solution  may  be  tabulated: 

4.9      grams  sulphuric  acid,  2.66   c.c.    (specific  gravity 

of  1.845). 
3.646  grams  hydrochloric  acid,  3.04  c.c.  (specific  gravity 

of  1.20). 

6.3      grams  nitric  acid,  4.44  c.c.  (specific  gravity  of  1 .42) . 
6.3      grams  oxalic  acid.     (Exists  in  solid  form.) 
4         grams  caustic  soda.     (Exists  in  solid  form.) 
5.61    grams  caustic  potash.     (Exists  in  solid  form.) 
5.3      grams  sodium  carbonate.     (Exists  in  solid  form.) 

(For  standardizing.) 

It  is  convenient  in  plant  practice  to  make  the  solutions  so  that 
1  c.c.  of  the  standard  solution  when  used  on  10  c.c.  of  cyanide 
solution  will  indicate  a  protective  alkalinity  or  an  acidity  equal 
to  1  pound  CaO  (unslacked  lime)  per  ton  of  solution.  For  this 
purpose  1000  c.c.  of  the  standard  solution  must  contain  its 
chemical  in  the  following  quantity: 

8.75    grams  sulphuric  acid,  4.74  c.c.  (specific  gravity  of 

1.845). 
6.51    grams  hydrochloric  acid,  5.42  c.c.  (specific  gravity 

of  1.20). 

11.25    grams  nitric  acid,  7.92  c.c.  (specific  gravity  of  1.42). 
11.25    grams  oxalic  acid.     (Exists  in  solid  form.) 
7.143  grams  caustic  soda.     (Exists  in  solid  form.) 
10.02    grams  caustic  potash.     (Exists  in  solid  form.) 
9.464  grams  sodium  carbonate.     (Exists  in  solid  form.) 
(For  standardizing.) 

The  action  and  use  of  alkalinity  have  been  indirectly  referred 
to  before  and  will  be  more  fully  treated  under  Alkalinity  and 
Lime. 


CHEMISTRY  OF  CYANIDE  SOLUTIONS  43 

E.   TOTAL  ALKALINITY 

The  "  total  alkalinity  "  of  a  cyanide  solution  is  that  alkalinity 
which  is  visible  in  the  presence  of  an  alkaline  indicator.  It  may 
be  said  to  be  that  of  the  protective  alkalinity  and  additionally 
of  the  cyanides  —  simple,  double,  and  otherwise. 

The  test  is  conducted  and  computed  exactly  the  same  as  in 
the  determination  for  protective  alkalinity,  except  that  the 
cyanide  and  zinc  are  not  rendered  neutral  and  inert  by  the 
addition  of  silver  nitrate  and  potassium  ferrocyahide. 

F.   FERROCYANIDES  AND  FERRICYANIDES 

Definition  and  Occurrence.  —  Iron  in  a  metallic  form  is 
attacked  by  cyanide  with  extreme  slowness,  but  most  of  the  iron 
compounds  are  more  readily  affected  and  dissolved.  Iron  may 
be  introduced  into  the  solution  in  this  way  by  contact  with 
corroded  pipes  and  iron  tanks,  or  iron  originating  in  the  milling 
process  and  subsequently  altered  to  a  compound  susceptible  of 
being  readily  dissolved  by  cyanide  solution.  Also  through  iron 
that  is  a  constituent  of  the  ore  as  an  oxide,  sulphate,  etc.2  from 
the  previous  decomposition  of  the  iron  or  other  pyrite,  or  in  the 
case  of  a  fresh  unweathered  pyrite  by  the  slow  alteration  when 
it  is  attacked  by  the  cyanide  or  alkali  of  a  solution,  especially 
in  the  presence  of  oxidation. 

The  combination  of  iron  (Fe)  and  cyanide  forms  an  infinite 
variety  of  compounds  under  the  head  of  ferrocyanides  and  ferri- 
cyanides,  in  the  simplest  form,  as: 

FeS04  +  6  KCN  =  K4Fe(CN)6  +  K2S04. 

In  which  the  ferrous  salt,  iron  sulphate  (FeS04),  when  brought 
into  contact  with  cyanide  forms  potassium  ferrocyanide 
(K4Fe(CN)6)  and  potassium  sulphate  (K2SO4),  while  the  ferro- 
cyanide may  eventually  be  changed  by  oxidation  to  ferricyanide 
(K3Fe(CN)6).  Iron  in  these  combinations  is  one  of  the  principal 
foreign  constituents  of  a  cyanide  solution.  The  ferrocyanides 
have  been  considered  as  reducers  through  utilizing  the  oxygen 
to  form  ferricyanides,  while  the  ferricyanides  have  been  con- 
sidered as  oxidizers  by  the  reversal  of  the  method  of  their  forma- 
tion. The  more  practical,  view  is  that  they  are  reducers  and 
thereby  harmful.  They  occur  in  the  solution  in  proportion  as 
the  iron  found  in  the  ore  in  a  state  subject  to  being  acted  upon 


44  TEXT  BOOK  OF  CYANIDE  PRACTICE 

by  cyanide  has  not  been  removed  or  oxidized  into  the  innocuous 
ferric  oxide  or  hydrates  by  water-washing,  alkaline  treatment, 
and  aeration.  When  occurring  in  small  quantities  their  in- 
fluence is  unnoticeable,  but  when  present  in  large  amounts  their 
effect  is  very  harmful,  reducing  the  percentage  of  extraction  or 
retarding  the  dissolution  of  the  precious  metals,  and  hindering 
the  precipitation  chemically  and  also  mechanically  through  the 
precipitation  of  ferrocyanide  compounds  in  the  zinc  box,  such 
as  zinc  potassium  ferrocyanide  and  similar.  When  solutions 
become  highly  charged  with  ferrocyanides  and  ferricyanides  so 
that  they  cannot  be  made  to  effect  the  extraction  made  in  labo- 
ratory tests  with  clean  solutions,  they  should  be  discarded,  which 
may  be  after  only  a  few  months  of  use.  However,  this  periodi- 
cal discarding  of  the  solutions  used  in  working  a  decomposed 
highly  pyritic  ore  can  usually  be  avoided  by  a  proper  removal, 
neutralization,  or  alteration  of  the  iron  by  water-washing, 
alkali,  or  aeration.  Or  the  solution  may  often  be  brought  to  a 
healthy  state  again  by  aeration  and  possibly  by  the  addition  of 
alkali.  Mercurous  or  mercuric  chloride  has  been  added  to  such 
solutions  with  the  effect,  through  the  activity  of  mercury  in 
combining  with  the  cyanogen  of  the  simple  and  double  cyanides 
and  including  the  ferrocyanides  and  ferricyanides,  to  form  a  potas- 
sium mercuric  cyanide  which  is  an  active  solvent  even  without 
oxygen,  and  probably  regenerates  the  cyanogen  of  ferrocyanides 
and  ferricyanides  into  the  active  mercuric  cyanide.  The  presence 
of  ferrocyanides  is  second  only  to  the  formation  of  alkaline 
sulphides  in  fouling  working  solutions,  and  the  part  that  each 
plays  in  such  a  fouling  effect  is  an  interesting  and  difficult  study. 
Determination.  —  The  simplest  method  of  determining  the 
ferrocyanides  and  ferricyanides  is  to  consider  all  the  iron  in 
solution  as  a  ferrocyanide.  The  cyanogen  is  decomposed  by 
evaporating  a  measured  quantity  of  solution  with  HNO3,  taking 
up  with  H2S04,  evaporating  almost  to  dryness,  and  taking  up 
with  water,  when  the  iron  may  be  determined  by  any  of  the 
usual  methods  for  determining  iron.  The  amount  of  iron  found 
is  multiplied  by  6.6  to  give  the  potassium  ferrocyanide  as 
K4Fe(CN)6,  as: 

4  (39.1)  +  55.85  +  6  (12  +  14) 

K4  Fe  (CN)6          368.25 


Fe  55.85 

55.85 


=  6.6. 


CHEMISTRY  OF  CYANIDE  SOLUTIONS          45 

G.  ALKALINE  SULPHIDES  AND  SULPHOCYANIDES 

Definition  and  Occurrence  of  Alkaline  Sulphides.  —  Alkaline 
or  soluble  sulphides,  as  potassium  sulphide  (K2S),  sodium  sul- 
phide (Na^S),  etc.,  are  often  formed  in  a  cyanide  solution,  or 
may  be  contained  in  small  quantities  in  the  cyanide  used.  They 
are  considered  to  occur  principally  through  the  decomposition 
of  a  metallic  sulphide  by  cyanide  or  alkali.  In  the  case  of 
treating  the  silver  sulphide  (Ag2S)  or  the  iron  pyrite  (FeS2)  by 
cyanide,  as: 

(  Ag2S  +  4  KCN  =  K2S  +  2  KAg.(CN)2. 
I  FeS2  +  6  KCN  =  2K2S  +  K2Fe(CN)6. 

The  decomposing  effect  of  alkali  with  the  formation  of  an  alka- 
line sulphide  is  shown  by  the  equation: 

FeS2  +  2  KOH  =  K2S  +  Fe(OH)2  +  S. 

The  general  effect  of  an  alkali  in  attacking  a  metallfc  sulphide 
is  to  form  an  alkaline  sulphide  with  the  sulphur  and  a  hydrate 
(as  Fe(OH)2)  of  the  base  remaining.  While  the  alkalis  do  not 
easily  act  upon  all  the  metallic  sulphides,  they  undoubtedly  have 
some  solvent  or  decomposing  effect  in  all  cases. 

Alkaline  Sulphides  and  Sulphocyanides  or  Thiocyanates.  - 
The  alkaline  sulphides  reduce  the  dissolving  power  of  the  solu- 
tion by  abstracting  the  oxygen  present,  probably  in  two  ways. 
First,  by  the  oxidation  of  the  alkaline  sulphide  into  an  alkaline 
sulphate,  as: 

K2S+4O  =  K2SO4; 

and  second,  by  forming  a  sulphocyanide  or  thiocyanate  (KCNS), 
as: 

K2S  +  KCN  +  H2O  +  O  =  KCNS  +  2  KOH. 

In  which  both  oxygen  and  cyanide  are  utilized  and  rendered 
useless  for  dissolving  purposes.  The  double  reaction,  first  into 
the  sulphide  and  then  into  the  thiocyanate,  may  be  stated  as: 

5  KCN  +  H2O  +  O  =2  KAg(CN)2+KCNS+2  KOH. 
=  K2Fe(CN)6+2KCNS+4KOH. 


Action  and  Removal  of  Alkaline  Sulphides.  —  The  alkaline 
sulphides  are  unstable  and  tend  to  reverse  the  equation  made 
by  their  formation,  precipitating  the  silver  as  a  sulphide,  and 
possibly  doing  the  same  to  a  slight  extent  with  the  gold,  or  at 


46  TEXT  BOOK  OF  CYANIDE  PRACTICE 

least  retarding  its  dissolution.  The  tendency  of  the  silver  to 
be  reprecipitated  in  this  way  increases  as  the  solution  becomes 
weaker  in  cyanide  in  obedience  to  the  law  of  mass  action;  which 
is,  that  in  the  case  of  one  substance  acting  chemically  on  another, 
the  action  will  proceed  until  the  mass  of  the  acting  substance  is 
overcome  by  the  mass  of  the  active  substance  formed,  at  which 
point  equilibrium  is  established,  and  if  the  mass  of  the  active 
substance  formed  is  then  increased  or  that  of  the  acting  substance 
decreased,  there  will  be  a  reversal  of  the  chemical  reaction  until 
chemical  equilibrium  is  again  established.  Consequently,  the 
mass  or  strength  of  the  cyanide  must  be  high  in  the  case  of  con- 
siderable alkaline  sulphides,  to  keep  them  from  reversing  the 
reaction  and  reprecipitating  the  silver.  This  is  one  of  the  reasons 
for  the  stronger  solutions  used  in  silver  plants.  The  principle 
can  be  shown  by  dissolving  silver  sulphide  (Ag2S)  in  strong 
cyanide  solution,  and  then  diluting  the  solution  until  a  precipi- 
tate of  the  Ag2S  forms.  In  plant  practice  too  weak  a  solution 
either  does  not  dissolve  the  silver  or  may  allow  it  to  be  repre- 
cipitated; while  an  accidental  wash  of  very  weak  solution  or 
water  before  dissolution  is  completed,  appears  to  stop  further 
extraction  with  strong  solution,  possibly  by  coating  the  metal 
or  mineral  with  a  hard,  insoluble  film  of  silver  sulphide  which  is 
extremely  difficult  to  dissolve. 

The  quantity  of  alkaline  sulphides  formed  in  treating  a  gold 
ore  is  small,  probably  increasing  as  the  amount  or  percentage 
of  pyrite  or  metallic  sulphide  (concentrate)  increases  and  as 
stronger  cyanide  or  alkaline  solutions  are  used.  The  alkaline 
sulphides  are  probably  removed  as  fast  as  formed  in  ordinary 
gold  ores  by  being  precipitated  and  discharged  in  the  pulp  residue 
as  an  insoluble  zinc  sulphide  (ZnS),  through  reacting  with  the 
zinc  potassium  cyanide  (K2Zn(CN)4)  formed  in  the  passage  of 
the  cyanide  solution  through  the  zinc  boxes,  as: 

K2Zn(CN)4  +  K2S  =  4  KCN  +  ZnS. 

Though  the  zinc  in  solution,  reacting  in  a  way  similar  to  that  of 
silver  when  reprecipitated,  is  a  valuable  ally  in  this  way,  it  may 
not  as  completely  remove  the  sulphides  as  desirable,  or  be  able 
to  cope  with  the  large  quantities  produced  in  treating  sulphide 
ores,  especially  the  sulphide  ores  of  silver.  A  lead  compound 
is  more  active  for  this  purpose,  precipitating  the  sulphur  as 


CHEMISTRY  OF  CYANIDE  SOLUTIONS          47 

an  insoluble  and  inert  lead  sulphide  (PbS).  Lead  acetate 
(Pb(C2H3O2)2)  has  principally  t>een  used  for  this  purpose.  Lith- 
arge (PbO),  the  oxide  of  lead,  has  also  been  employed,  but  being 
insoluble  cannot  be  conveniently  used.  The  reaction  in  the 
case  of  using  lead  acetate  is: 

Pb(C2H3O2)2  +  4  KOH  =  K2PbO2  +  2  K(C2H3O2)  +  2  H2O. 
K2PbO2  +  K2S  +  2  H2O  =  PbS  +  4  KOH. 

Mercury  dissolved  in  amalgamating  in  cyanide  solution  or 
added  as  a  soluble  salt  is  even  more  active  in  precipitating  the 
alkaline  sulphides  than  lead  compounds,  and  mercurous  (HgjjC^) 
or  mercuric  chloride  (HgCl2)  has  been  used  for  this  purpose. 
Oxidation  of  the  alkaline  sulphides  into  sulphates  or  thiocyanates, 
by  aeration  of  the  solution  and  charge,  will  cause  a  solution  con- 
taining alkaline  sulphides  to  regain  its  solvent  ability.  It  is 
this  tendency  of  the  alkaline  sulphides  to  oxidize,  this  strong 
reducing  action  in  utilizing  the  oxygen  that  is  necessary  in  dis- 
solving the  gold  and  silver,  that  causes  the  poor  or  retarded 
extraction  from  ores  giving  rise  to  the  alkaline  sulphides.  The 
sulphides  are  often  precipitated  in  the  zinc  boxes  as  a  zinc  or 
silver  sulphide,  the  sulphur  of  which  may  give  trouble  in  the 
clean-up.  There  is  a  possibility  that  some  of  the  influence  that 
running  a  solution  through  the  zinc  boxes  has  on  cleansing  it 
and  making  it  a  more  active  solvent  is  due  to  the  precipitation 
of  the  soluble  sulphides  by  the  zinc  dissolved  and  other  influences 
in  the  passage  through  the  boxes. 

Application  of  Lead  Acetate.  —  Lead  acetate  for  the  purpose 
of  precipitating  the  alkaline  sulphides  is  not  often  used  in  gold 
plants,  for  small  amounts  of  the  sulphides  are  not  harmful  and 
are  removed  by  the  zinc.  It  is  used  in  most  silver  plants,  though 
it  does  not  appear  necessary  unless  working  on  sulphide  ores. 
Since  the  alkaline  sulphides  are  generally  oxidized  or  changed 
to  the  thiocyanates  in  a  short  time,  solutions  in  which  they  have 
formed  do  not  often  show  them,  but  rather  the  resulting  thio- 
cyanates, the  determination  of  which  —  since  only  a  part  of  the 
alkaline  sulphides  are  changed  to  the  thiocyanates  —  does  not 
appear  to  be  of  practical  value  in  the  matter  of  removing  the 
soluble  sulphides.  Consequently,  the  amount  of  lead  acetate 
or  other  precipitant  to  be  used  can  only  be  determined  in  an 
empirical  way,  by  attempting  to  learn  its  influence  on  the  ex- 


48  TEXT  BOOK  OF  CYANIDE  PRACTICE 

traction  and  by  examining  the  solution  for  the  alkaline  sulphides 
before  time  has  been  allowed  them  to  oxidize.  The  tendency 
of  the  solution  to  foul  against  further  dissolution  of  the  precious 
metals  until  aerated,  its  reducing  power,  and  its  efficiency  in 
competition  with  newly-made  solutions  are  studied  in  this  con- 
nection. Most  plants  treating  sulphide  silver  ores  use  a  half- 
pound  or  less  of  lead  acetate  per  ton  of  ore  treated;  some  use  as 
high  as  a  few  pounds.  It  is  prepared  as  a  solution  to  be  added 
to  the  agitation  charge  or  sprinkled  throughout  the  sand  to  be 
leached,  or  less  often -added  to  the  solution  in  some  convenient 
manner. 

Test  for  Alkaline  Sulphides.  —  The  presence  of  alkaline 
sulphides  may  be  determined  by  agitating  200  c.c.  of  the  solu- 
tion with  a  small  quantity  of  lead  carbonate  (PbCO3).  A  black 
precipitate  of  lead  sulphide  will  indicate  the  presence  of  alkaline 
sulphides.  Another  method  of  testing  consists  of  preparing  a 
solution  of  nitroprusside  by  adding  a  little  nitric  acid  to  a  solu- 
tion of  ferro  or  ferricyanide  of  potassium.  Add  a  few  drops  of 
the  nitroprusside  solution  to  the  cyanide  solution.  If  alkaline 
sulphides  are  present,  even  in  minute  quantities,  the  solution 
will  assume  a  brilliant  purple  color. 


H.    AVAILABLE   CYANIDE 

Definition.  —  "  Available  cyanide  "  has  been  given  as  an  in- 
definite term  referring  to  the  "  solvent  ability  "  of  a  cyanide 
solution  to  dissolve  the  precious  metals.  This  ability  is  due  and 
proportional  to  the  amount  of  the  free  or  simple  cyanide  mainly, 
to  some  extent  to  the  easily-decomposed  double  cyanides  and 
perhaps  the  hydrocyanic  acid,  and  to  little  if  any  extent  to  the 
other  cyanogen  compounds.  It  is  indirectly  affected  by  many 
other  things,  as  the  protective  alkalinity,  the  amount  of  oxygen 
available,  the  quantity  and  nature  of  the  foreign  constituents, 
and  the  substances  in  combination  with  the  cyanogen.  This 
will  indicate  that  an  estimation  of  the  constituents  and  char- 
acteristics usually  determined  will  not  clearly  indicate  the  solvent 
ability  or  efficiency  of  a  solution.  Consequently  the  available 
cyanide  or  the  solvent  ability  cannot  be  reduced  to  any  terms. 
It  can  only  be  compared  with  a  so-called  standard,  for  which  a 
new  or  freshly-made-up  solution  may  be  taken. 


CHEMISTRY  OF  CYANIDE  SOLUTIONS          49 

Test  for  Available  Cyanide.  —  The  usual  method  of  estimating 
the  available  cyanide  or  dissolving  efficiency  is  to  run  compara- 
tive laboratory  tests  on  two  portions  of  the  same  sample  of  ore, 
treating  one  with  the  mill  solution  to  be  tested  and  the  other 
with  a  new  solution.  Care  should  be  taken  that  the  amount  of 
sample  taken,  the  volume  of  solution  used,  and  the  strength  of 
solution,  etc.,  is  exactly  similar  in  the  duplicate  tests.  Where 
these  are  made  frequently  a  large  sample  of  50  to  100  pounds 
may  be  prepared  and  check  tests  made  on  it  with  fresh  solution, 
after  which  tests  may  be  made  on  portions  of  the  sample  with 
mill  solutions  whenever  desired.  This  will  give  the  results  with 
only  one  test,  but  most  operators  will  prefer  the  first  method, 
taking  for  their  sample  the  discard  from  the  sample  for  assay 
taken  of  a  working  charge,  and  thereby  checking  the  working 
extraction  by  laboratory  tests. 

L    CYANATES  AND  TOTAL  CYANOGEN 

Cyanic  acid  has  the  composition  HCNO.  In  cyanates  the 
H  is  replaced  by  a  metal  or  base  as  KCNO.  The  decomposition 
of  cyanide  through  oxidation  in  a  solution  may  be  considered  as 
into  a  cyanate,  which  is  without  effect  in  the  practical  working 
of  the  process. 

"  Total  cyanogen  "  is  a  term  that  has  been  used  to  indicate 
or  refer  to  all  the  cyanogen  or  CN  radical  present  in  a  solution, 
in  any  form  whatever,  such  as  in  the  simple  and  double  cyanides, 
the  hydrocyanic  acid,  and  the  ferrocyanides,  ferricyanides,  thio- 
cyanates,  cyanates,  etc. 

J.   REDUCING  POWER 

Cyanide  solutions  vary  in  their  reducing  power,  in  the  tendency 
for  substances  in  the  solution  to  oxidize  and  thus  abstract  the 
dissolved  oxygen  that  should  be  available  for  the  dissolution  of 
gold  and  silver.  The  reducing  power  can  be  determined  in  a 

(N\ 
-jrl  solution  of 

potassium  permanganate  (KMn04),  containing  3.16  grams  of 
the  chemical  in  one  liter  of  water.  Any  convenient  but  standard 
amount  of  the  cyanide  solution  may  be  taken  and  acidulated 
by  a  standard  amount  of  sulphuric  acid,  to  which  the  standard 


50     TEXT  BOOK  OF  CYANIDE  PRACTICE 

potassium  permanganate  solution  should  be  added,  until  the 
color  no  longer  disappears.  The  results,  as  stated  in  the  amount 
of  decinormal  potassium  permanganate  solution  used  on  a  con- 
stant amount  of  cyanide  solution,  are  recorded  and  studied  in  a 
comparative  way,  to  learn  the  advisability  or  necessity  of  aerating 
the  solution  and  ore,  and  any  changes  that  may  take  place  in  the 
reducing  power  of  the  solution  or  ore. 

K.   ASSAY  OF  METALS  IN  CYANIDE  SOLUTION 

Classification  of  Methods  for  Gold  and  Silver.  —  The  usual 
methods  of  assaying  cyanide  solution  for  gold  and  silver  fall 
naturally  into  four  classes: 

A.  Evaporation  of  the  solution  in  a  tray  or  boat  of  lead  foil, 
followed  by  the  cupellation  of  the  residue  and  lead  tray. 

B.  Evaporation  of  the   solution  with   litharge,    addition  of 
suitable  fluxes,  fusion  in  the  assay  furnace,  and  cupellation. 

C.  Precipitation  of  the  precious  metals,  nitration,  incinerating 
the  filter  and  its  precipitate,  fluxing  the  residue,  melting,  and 
cupeling. 

D.  Precipitation  of  the  precious  metals  with  a  large  amount 
of  lead,  removing  precipitate  from  the  solution,  and  cupeling 
without  fusion  —  the  Chiddy  method. 

A .  Lead  Tray  Evaporation.  —  A  block  of  wood  about  f  inch 
thick,  If  inches  wide,  and  2J  inches  long  is  prepared.  The  lead 
foil  is  cut  into  strips  to  be  folded  about  this  block  into  a  tray 
f  inch  deep.  A  test  tube  is  graduated  by  a  file  mark  or  a  sticker 
to  hold  1  assay  ton  of  solution  as  indicated  by  29.166  c.c.  of  solu- 
tion run  in  from  a  burette.  By  means  of  this  measuring  tube, 
1  assay  ton  of  the  solution  is  placed  in  the  tray,  which  is  set  on  a 
piece  of  asbestos  board  on  a  hot  plate  to  be  evaporated  to  dry- 
ness.  After  evaporation  the  tray  is  folded  into  a  compact  mass 
and  placed  in  a  cupel  to  be  cupeled.  This  method  does  not 
give  extremely  accurate  results,  through  the  spitting  of  the  solu- 
tion while  evaporating  and  through  the  impurities  in  the  solution 
affecting  the  subsequent  cupellation.  It  has  the  further  disad- 
vantage of  requiring  considerable  time  and  enabling  only  a  small 
amount  of  solution  to  be  taken  for  assay  —  though  larger  trays 
taking  3  assay  tons  may  be  conveniently  used.  However,  being 
a  simple  method  it  is  often  employed. 


CHEMISTRY  OF  CYANIDE  SOLUTIONS          51 

B.  Evaporation  with  Litharge,  etc.  —  Any  measured  quantity 
of  the  solution  may  be  taken,  usually  5  to  10  assay  tons.     This 
is  placed  in  a  porcelain  evaporating  dish,  covered  with  from  20 
to  40  grams  of  litharge,  to  lessen  the  tendency  to  spit,  and  evapo- 
rated without  boiling  for  the  same  purpose.     The  residue  after 
evaporation  is  transferred  to  an  assay  crucible,  to  which  is  added 
the  fluxes  necessary  to  produce  the  usual  assay  fusion,  which 
may  consist  of  15  grams  bicarbonate  of  soda,  5  grams  borax 
glass,  4  grams  silica  or  more  of  powdered  glass,  and  1  gram  flour 
as  a  reducer.     The  flux  may  be  varied  in  any  way  that  will  give 
a  satisfactory  fusion.     The  amount  of  silica  or  powdered  glass 
used  should  be  just  sufficient  to  prevent  the  charge  from  attack- 
ing the  crucible.     The  amount  of  flour  or  reducer  should   be 
varied  to  give  a  button  of  the  desired  size.     The  lead  button 
obtained   from   the  fusion  is  cupeled,  etc.,  in  the  usual  way. 
Evaporation  with  litharge  is  supposed  to  give  the  most  exact 
results  of  the  different  methods  in  use.     It  has  been,  and  will 
continue  to  be,  the  method  by  which  all  other  methods  will  be 
checked,  but  owing  to  the  time  and  labor  involved  is  not  used 
in  ordinary  work. 

C.  Precipitation,   Incinerating,   Fusing,   etc.  —  This   method 
involves  the  precipitation  of  the  precious  metals  from  the  solu- 
tion by  the  addition  of  a  metal,  metallic  salt,  or  other  substance; 
the  filtering  off  of  the  precipitate  followed  by  incinerating  it 
and  the  filter;  and  the  fluxing  and  fusing  of  the  residue  as  in  the 
usual  fire  assay.     Numerous  reliable  methods  have  been  used, 
each  of  which  has  its  advocates.     They  are  the  methods  that 
were  formerly  used  in   plant  practice,  but  which  have  largely 
been  superseded  by  the  Chiddy  method.     The  following  is  one 
of  the  simplest  and  most  practical  of  these  methods.     Take  10 
assay  tons  of  the  cyanide  solution  in  a  beaker.     Add  4  grams  of 
zinc  dust  on  point  of  spatula.     Stir  vigorously.     Allow  to  stand 
for  a  few  minutes  and  again  stir.     Finally  add  about  10  c.c.  of 
commercial  H2SO4  and  stir.     After  action  has  ceased,  add  more 
H2SO4  if  needed,  until  sulphuric  acid  is  in  excess  and  zinc  is  all 
dissolved,  which  will  be  indicated  by  no  more  action  when  a 
small  quantity  of  the  acid  is  added.     Filter  and  incinerate  filter 
and  precipitate  by  placing  in  an  assay  crucible  and  setting  in 
muffle  or  furnace.     Add  suitable  flux  after  incinerating  and  cool- 
ing, which  may  consist  of  10  grams  litharge,  10  grams  bicar- 


52  TEXT  BOOK  OF  CYANIDE  PRACTICE 

bonate  of  soda,  3  grams  silica  or  more  of  powdered  glass,  and  1 
gram  flour.     Fuse,  cupel  lead  button,  etc. 

D.  Precipitation  with  Direct  Cupellation  —  the  Chiddy 
Method.  —  The  Chiddy  method  with  various  modifications  is 
now  generally  used,  as  it  is  an  easily-handled,  quick,  and  reliable 
method  for  gold  and  silver.  Place  5  to  10  assay  tons  of  the 
solution  in  a  beaker.  Heat  nearly  to  boiling.  Add  before  or 
during  the  heating,  10  c.c.  of  a  clear  saturated  solution  of  lead 
acetate  (Pb(C2H302)2.3  H20)  and  .5  gram  zinc  dust.  One  part 
of  lead  acetate  will  dissolve  in  2  parts  of  water,  while  any  excess 
will  remain  undissolved  in  the  bottom  of  the  bottle  or  vessel 
holding  the  solution.  Stir  well  and  bring  nearly  to  boiling. 
Allow  to  heat  for  several  minutes.  Stir  again  and  add  15  c.c. 
of  commercial  HC1,  and  continue  heating.  After  effervescence 
has  ceased,  add  more  HC1  until  the  absence  of  action  shows  that 
the  zinc  is  dissolved  and  the  acid  is  in  excess.  The  lead  has  now 
settled  into  a  sponge  which  should  be  tapped  together  and 
pressed  into  a  mass  with  a  glass  rod,  the  solution  poured  off,  and 
the  lead  washed  once  or  more  by  decantation.  The  lead  is 
pressed  into  a  compact  mass  with  a  glass  rod  or  the  fingers  to 
remove  the  water.  It  is  placed  on  a  piece  of  lead  foil  1J  inches 
square,  which  is  folded  to  allow  the  steam  to  escape  at  the  top, 
and  is  placed  in  a  hot  cupel  for  cupellation. 

The  principal  trouble  encountered  in  using  this  method  is  the 
tendency  of  the  lead  to  break  up  instead  of  agglomerating,  and 
thus  become  lost  in  the  decanting.  This  may  be  prevented  to 
some  extent  by  not  allowing  the  solution  to  come  to  a  boil. 
Another  method  is  to  introduce  into  the  solution  a  piece  of 
aluminum  from  1  to  1J  inches  square  and  TV  to  |  inch  thick, 
which  will  more  readily  collect  the  lead,  and  can  easily  be  re- 
moved before  cupellation.  Where  the  lead  breaks  up,  it  may 
be  finally  transferred  to  the  point  of  a  small  filter  paper,  which 
should  be  dried  before  cupeling.  A  simple  expedient  is  to 
transfer  or  wash  the  lead  into  a  small  lead  foil  tray  an  inch  or 
more  square,  drain  the  moisture  through  a  folded  corner,  and 
dry  tray  before  cupeling.  Where  zinc  dust  is  not  available  a 
somewhat  larger  amount  of  the  shavings  may  be  used.  This 
method  gives  good  results  with  very,  weak  solutions,  but  it  is 
advisable  to  have  some  strong  solution  on  hand  and  bring  very 
weak  solutions  up  to  not  to  exceed  .5  per  cent  (10  pounds)  KCN. 


CHEMISTRY  OF  CYANIDE  SOLUTIONS  53 

L.    ASSAY  OF  BASE  METALS  IN  SOLUTION 

The  base  metals  in  a  cyanide  solution,  such  as  iron,  copper, 
lead,  zinc,  etc.,  may  be  determined  in  any  of  the  usual  ways  by 
first  decomposing  the  cyanogen.  This  may  be  performed  by 
adding  to  a  measured  quantity,  of  solution,  as  100  to  300  c.c., 
from  5  to  10  c.c.  HNO3  and  the  same  amount  of  H2SO4,  evapo- 
rating to  dryness,  and  taking  up  with  a  few  cubic  centimeters 
of  H2SO4  diluted  with  water.  This  gives  the  metals  as  sul- 
phates for  determination  in  the  usual  manner. 


CHAPTER  VI 
ALKALINITY  AND  LIME 

Definition  and  Properties  of  Lime.  —  Lime  (CaO)  is  an  alka- 
line earth,  an  oxide  of  the  metal  calcium  (Ca).  Neither  calcium 
nor  its  oxide  (lime)  occurs  free  in  nature.  Lime  is  prepared  by 
burning  or  calcining  limestone,  which  when  pure  is  calcium  car- 
bonate (CaCO3)  or  carbonate  of  lime,  thereby  driving  off  the 
carbonic  acid  (CO2)  and  leaving  lime  (CaO)  in  unfused  lumps 
in  the  form  of  the  original  stone.  In  this  state  it  is  called  burnt 
lime,  unslacked  lime,  quicklime,  caustic  lime,  calcium  oxide,  or 
dehydrated  or  anhydrous  calcium  oxide  or  lime.  When  this 
lime  is  exposed  to  the  atmosphere,  it  attracts  moisture  and  falls 
into  a  powder  with  a  rapidity  dependent  upon  the  amount  of 
moisture  in  the  air  and  the  quality  of  the  lime,  more  rapidly  as 
the  quality  of  the  lime  or  absence  of  impurities  becomes  higher 
and  the  calcining  process  has  been  carried  to  the  proper  point. 
This  process  is  called  air-slacking. 

When  lime  (CaO)  is  brought  into  contact  with  water  (H20), 
it  decomposes  the  water  with  the  evolution  of  much  heat  —  a 
process  called  slacking  —  to  form  Ca(OH)2,  known  as  slacked 
lime,  or  calcium  or  lime  hydroxide  or  hydrate;  it  is  the  same  prod- 
uct as  is  formed  by  air-slacking.  The  term  "  lime  "  in  connec- 
tion with  the  cyanide  process  always  refers  —  unless  otherwise 
noted  —  to  the  equivalent  of  unslacked  lime  (CaO),  whether  the 
lime  is  slacked  before  use  or  not. 

Lime  after  being  slacked  readily  mixes  with  water  to  form  a 
smooth  and  liquid  paste  called  "  milk  of  lime."  A  filtered  or 
clear  saturated  solution  of  lime  is  called  "  lime  water."  This,  as 
representing  the  maximum  solubility  of  lime  in  water,  contains 
about  1  part  unslacked  lime  (CaO)  in  800  parts  of  water,  equal 
to  .125  per  cent  or  2J  pounds  per  ton  of  water.  This  is  equal  to 
1  part  of  slacked  lime  (Ca(OH)2)  in  600  parts  of  water,  but  the 
results  are  invariably  stated  as  unslacked  lime.  By  the  use  of 
an  excess  of  lime,  cyanide  solutions  can  be  made  to  show  a  pro- 

54 


ALKALINITY  AND  LIME  55 

tective  alkalinity  of  higher  than  .125  per  cent  (2J  pounds)  CaO, 
but  probably  not  more  than  .15  per  cent  (3  pounds);  this  is  due 
to  the  alkalinity  of  other  substances,  more  especially  those  result- 
ing from  chemical  reactions. 

Uses  of  Lime  and  Alkalinity  in  the  Cyanide  Process.  —  Lime 
and  alkalinity  have  no  solvent  action  upon  the  precious  metals, 
but  enter  into  numerous  reactions  occurring  in  the  cyanide  proc- 
ess. Through  these  they  protect  the  cyanide  from  being  de- 
stroyed or  decomposed,  mainly  by  entering  into  the  combinations 
that  cyanide  would  otherwise  enter;  by  liberating  or  regenera- 
ting cyanide  through  replacing  it  in  compounds;  and  by  pre- 
cipitating or  rendering  inactive  substances  that  may  interfere, 
thus  keeping  the  solution  clean  and  in  excellent  condition  for 
dissolving  the  precious  metals  out  of  the  ore  and  precipitating 
them  in  the  zinc  boxes.  A  further  use  of  lime  and  alkalinity  is 
as  a  solvent  upon  base  metals  and  compounds,  thereby  better 
liberating  the  precious  metals  from  the  chemical  combination 
or  mechanical  alloy  or  covering  for  easy  dissolution.  In  doing 
this  lime  acts  as  an  alkali,  and  any  alkali  could  be  used  with  more 
or  less  advantage  for  this  purpose,  but  lime  is  almost  exclusively 
used  owing  to  its  cheapness  and  that  its  properties  and  reactions 
are  preferable  to  those  of  the  other  alkalis  which  have  been  used, 
principally  caustic  soda  and  to  a  slight  extent  caustic  potash. 
In  illustrating  the  chemical  reactions  of  the  cyanide  process  it 
is  customary  to  use  caustic  potash  (KOH)  as  the  alkali  formed 
or  decomposed,  probably  because  the  K  of  the  alkali  is  convenient 
to  add  to  the  CN  as  KCN.  The  student  should  bear  in  mind 
that  the  use  of  caustic  potash  in  this  way  is  as  a  generic  or  class 
term  referring  to  alkalis  in  general  and  not  to  caustic  potash  in 
particular,  consequently  K,  Na,  and  Ca  may  be  considered  to 
have  similar  properties  when  united  to  CN  as  a  cyanide  or  to  OH 
as  an  alkali,  and  likewise  to  a  more  or  less  extent  with  the  other 
alkaline  earths  and  metals. 

Lime  also  acts  physically  in  addition  to  chemically.  It  is 
used  in  connection  with  slime  treatment  for  the  purpose  of 
causing  the  light,  feathery,  suspended  slime  to  agglomerate  and 
settle  rapidly  for  decantation  or  pulp-thickening  purposes. 
This  subject  is  treated  under  Slime  Treatment  and  Agitation. 

Neutralization  of  Metallic  Salts.  —  The  main  use  of  lime  is  as 
a  neutralizer  of  the  acid  and  metallic  salts  formed  in  the  ore 


56  TEXT  BOOK  Of  CYANIDE  PRACTICE 

through  the  oxidation  and  decomposition  of  the  metallic  sulphides. 
The  principal  stages  in  the  decomposition  of  iron  pyrite  may  be 
adapted  from  those  given  by  W.  A.  Caldecott,*  as: 

(1).  FeS2.  Iron  pyrite. 

(2).  FeS  +  S.  Ferrous  sulphide  and  sulphur. 

(3).  FeS04  +  H2SC>4.     Ferrous  sulphate  and  sulphuric  acid. 

(4).  Fe2(S04)3.  Normal  ferric  sulphate. 

(5).  2Fe203.S03.  Basic  ferric  sulphate. 

(6).  Fe2O3.zH2O.  Ferric  hydrate. 

(7).  Fe203.  Ferric  oxide. 

A  fresh  unoxidized  metallic  sulphide,  as  an  iron  pyrite,  is  but 
little  acted  upon  by  cyanide  solution.  But  in  a  weathering  and 
partially  decomposing  iron  pyrite  this  reaction  probably  occurs: 

FeS2  +  H20  +  7  0  =  FeSO4  +  H2S04. 

The  sulphuric  acid  (H2SO4)  formed,  if  brought  into  contact  with 
the  cyanide,  will  destroy  it  through  forming  hydrocyanic  acid 
(HCN),  as: 

H2SO4  +  2  KCN  -  2  HCN  +  K2SO4. 

The  decomposition  into  hydrocyanic  acid  may  be  prevented  by 
washing  the  soluble  sulphuric  acid  out  of  the  ore  before  the 
application  of  cyanide,  by  a  neutralizing  alkali  wash,  or  less 
perfectly  by  a  protective  alkalinity  in  the  cyanide  solution,  as: 

H2SO4  +  Ca(OH)2  =  CaSO4  +  2  H2O. 

The  calcium  sulphate  (CaS04)  formed  being  an  insoluble  salt 
harmless  to  the  cyanide.  If  caustic  soda  (NaOH)  is  used,  the 
resulting  sodium  sulphate  (Na2SO4)  is  very  soluble.  The  potas- 
sium sulphate  (K2SO4)  resulting  from  the  use  of  caustic  potash 
(KOH)  is  also  very  soluble.  Any  hydrocyanic  acid  will  be  re- 
generated in  the  presence  of  lime  or  protective  alkalinity  into  a 
cyanide,  as: 

HCN  +  KOH  =  KCN  +  H2O. 

The  ferrous  sulphate  (FeS04)  formed  in  the  first  equation 
of  the  previous  paragraph  will  destroy  cyanide,  as : 

FeS04  +  2  KCN  =  Fe(CN)2  +  K2SO4. 
Fe(CN)2  +  4  KCN  =  K4Fe(CN)6. 

In  which  the  simple  iron  cyanide  (Fe(CN)2),  if  it  is  formed  at  all, 
*  Proc.  Chemical  and  Metallurgical  Soc.  of  S.  A.,  Vol.  2. 


ALKALINITY  AND  LIME  57 

is  immediately  changed  into  the  species  of  double  cyanide,  the 
ferrocyanide  (K4Fe(CN)6).  Further  complex  reactions  between 
the  ferrocyanide  and  the  ferrous  sulphate  may  result  in  the  for- 
mation of  Prussian  blue  (Fe4(Fe(CN)6)3),  which  will  give  a  blue 
color  to  the  solution  and  deposit  small  quantities  of  the  dark- 
blue  compound  in  the  ore,  tanks,  and  piping,  acting  as  a  sign 
that  the  neutralization  has  been  poorly  carried  out. 

The  ferrous  sulphate  is  very  soluble  and  may  be  washed  out 
or  may  be  neutralized  into  the  harmless  insoluble  calcium  sulphate 
by  means  of  lime,  or  into  other  harmless  salts  by  other  alkalis,  as : 

FeSO4  +  Ca(OH)2  =  CaSO4  +  (FeO  +  H2O  or  Fe(OH)2). 

The  ferrous  oxide  (FeO),  if  it  does  form,  is  hydrolized  into  the 
ferrous  hydroxide  or  hydrate  (Fe(OH)2),  a  white  precipitate 
which  turns  a  dirty  green,  is  insoluble,  and  is  easily  oxidized  into 
the  insoluble  ferric  oxide  (Fe2O3),  thus  acting  as  a  strong  reducer 
or  deoxidizer  in  the  solution  and  ore.  The  ferrous  hydroxide  or 
hydrate  is  acted  upon  by  cyanide,  as: 

Fe(OH)2  +  6  KCN  =  K4Fe(CN)6  +  2  KOH. 

It  is  probably  the  principal  source  of  loss  through  the  reaction 
between  iron  and  cyanide,  and  the  hardest  iron  interference  to 
remove.  The  loss  of  cyanide  is  reduced  by  affording  every 
means  for  the  ferrous  hydrate  (Fe(OH)2)  to  be  oxidized  into  the 
ferric  oxide  (Fe2O3),  which  is  unacted  upon  by  cyanide.  The 
use  of  aeration  or  oxygen  besides  reducing  the  cyanide  consump- 
tion, increases  the  extraction  of  the  precious  metals  by  supplying 
the  oxygen  that  would  otherwise  be  abstracted  by  the  iron  from 
the  solution  or  ore.  To  meet  such  conditions  it  may  be  necessary 
to  pump  air  through  the  charge  before  or  during  treatment. 

If  the  ferrous  sulphate  (FeSO4)  is  not  removed  when  formed, 
it  will  oxidize  into  the  poorly  soluble  normal  ferric  sulphate 
(Fe2(SO4)3),  and  from  that  into  the  insoluble  basic  ferric  sulphate 
(2Fe2O3.SO3),  both  of  which  will  react  with  cyanide  and  thereby 
cause  a  high  consumption  in  the  same  manner  as  ferrous  sulphate, 
but  in  the  presence  of  alkali  these  are  probably  converted  or 
oxidized  into  the  hydrous  ferric  oxides,  as: 

(  Fe2(SO4)3  +  6  KOH  ==  Fe2O3.3  H2O  +  3  K2S04. 
I  2  Fe2O3.SO3+2  KOH  =  2  Fe2O3.H2O  +  K2SO4. 


58  TEXT  BOOK  OF  CYANIDE  PRACTICE 

The  hydrous  ferric  oxides  or  ferric  hydrates  have  the  formula 
Fe2O3.xH2O  in  which  x,  representing  the  number  of  molecules  of 
H20,  is  variable  and  indeterminate.  The  ferric  hydrates  are 
formed  from  the  ferrous  and  ferric  salts  —  as  the  sulphates  — 
by  the  action  of  alkali.  Some  of  them  are  to  some  extent  soluble 
and  act  upon  cyanide,  others  do  not.  Taken  as  a  whole,  they 
may  be  considered  to  be  insoluble  and  harmless  to  cyanide,  more 
especially  in  the  presence  of  alkalinity  and  aeration  which  in- 
creases these  properties  or  carries  the  compound  nearer  to  the 
inert  ferric  oxide  (Fe203)  —  ferric  hydrate  less  its  water  of  com- 
bination. The  red  or  blood  color  sometimes  noted  in  solutions 
is  usually  due  to  a  soluble  iron  or  manganese  compound  which 
the  addition  of  alkali  or  a  continued  aeration  will  precipitate  as 
an  inert  ferric  or  other  hydrate.  The  decomposition  of  sulphide 
ores  may  result  in  the  formation  of  sulphates  of  other  metals, 
such  as  magnesium  and  aluminium,  which  would  interfere  in  a 
way  similar  to  the  iron  salts,  but  the  use  of  lime  or  alkalinity 
converts  them  into  hydroxides  that  are  harmless. 

Lime  and  Alkalinity  in  Zinc  Precipitation.  —  Lime  and  alka- 
linity play  an  important  part  in  the  zinc  precipitation  of  the 
precious  metals.  In  weak  cyanide  solution  the  zinc  in  solution 
may  be  considered  to  take  the  form  of  a  hydroxide  (Zn(OH)2),  or 
the  single  zinc  cyanide  (Zn(CN)2),  both  of  which  are  insoluble  in 
water  and  only  slightly  soluble  in  weak  cyanide  solution.  In 
strong  cyanide  solution  the  zinc  may  be  considered  to  exist  as  the 
double  zinc  potassium  cyanide  (K2Zn(CN)4)  which  is  highly 
soluble,  and  in  alkaline  solutions  of  the  alkalis  as  a  zincate 
(Zn(KO)2)  which  is  also  very  soluble.  With  weak  solution  the 
zinc  shavings  will  be  more  or  less  coated  with  zinc  hydroxide  and 
zinc  cyanide,  so  that  little  dissolution  of  the  zinc  takes  place 
under  conditions  to  replace  the  gold  in  the  double  gold  potassium 
cyanide  (KAu(CN)2),or  to  chemically  set  up  the  electric  currents 
that  assist  in  depositing  the  gold.  This  results  in  poor  precipi- 
tation and  the  formation  of  the  white  precipitate  of  the  zinc 
boxes,  consisting  mainly  of  zinc  hydroxide  and  zinc  cyanide. 
The  use  of  a  strong  cyanide  solution  dissolving  the  white  pre- 
cipitate of  hydroxide  and  simple  cyanide  to  form  the  soluble 
double  cyanide  and  actively  dissolving  the  zinc,  keeps  it  clean 
and  promotes  good  precipitation.  Lime  or  alkalinity  may  be 
used  in  the  same  way  as  cyanide  for  this  purpose,  with  the  ex- 


ALKALINITY  AND  LIME  59 

ception  that  the  soluble  zincate  is  formed  instead  of  the  double 
cyanide.  The  subject  is  further  discussed  and  the  reactions 
given  under  Precipitation. 

While  a  protective  alkalinity  is  usually  necessary  for  good 
precipitation,  at  least  with  weak  solution,  too  high  an  alkalinity 
must  be  avoided  as  it  causes  an  excessive  action  on  the  zinc,  as: 

Zn  +  2  KOH  =  Zn(KO)2  +  2  H, 

resulting  in  an  increased  consumption  of  zinc  and  the  production 
of  much  hydrogen,  which  may  cause  an  undesirable  disturbance 
in  the  zinc  boxes  and  poor  precipitation,  by  the  entangled  hydro- 
gen bubbles  preventing  good  contact  between  the  solution  and 
the  zinc.  Too  high  a  protective  alkalinity  may  cause  a  deposi- 
tion of  lime  salts  in  the  zinc  boxes,  covering  the  zinc  with  a 
flocculent  or  hard  precipitate  which  interferes  with  precipitation, 
and  increases  the  bulk  of  the  clean-up  and  melt,  even  with  sul- 
phuric acid  treatment,  for  the  calcium  sulphate  formed  is  very 
insoluble. 

Lime  as  a  Neutralize?  of  Carbonic  Acid.  —  Carbonic  acid 
(C02)  decomposes  cyanide  into  hydrocyanic  acid,  as: 

KCN  +  C02  +  H20  =  HCN  +  KHCO3. 

The  hydrocyanic  acid  liberated  is  regenerated  into  cyanide  by 
any  alkali  present,  or  the  carbonic  acid  is  itself  neutralized,  as: 

(  HCN  +  KOH  =  KCN  +  H20. 
I  CO2  +  KOH  =  KHCO3. 

The  source  of  carbonic  acid  or  carbon  dioxide  may  be  the  atmos- 
phere, the  air  used  in  agitation  and  aeration,  organic  matter, 
carbonate  ores,  etc.  The  air  used  in  agitation,  besides  perhaps 
increasing  the  cyanide  consumption  to  a  small  extent  through 
its  carbonic  acid,  increases  the  consumption  of  alkali  very 
materially,  forming  insoluble  calcium  carbonate  (CaC03)  in  the 
case  of  lime.  This  coats  or  clots  the  filtering  canvases  of  the 
leaf  filters  so  that  they  must  be  treated  with  dilute  hydrochloric 
acid  to  dissolve  out  the  calcium  carbonate  as  a  soluble  calcium 
chloride.  A  high  protective  alkalinity  is  not  used  in  many 
plants  for  this  reason  alone.  The  use  of  a  high  protective 
alkalinity  may  also  give  trouble  in  this  way,  by  coating  and 
gradually  closing  the  solution  pipes  with  a  deposit  of  calcium 
carbonates  and  other  alkaline  earths. 


60  TEXT  BOOK  OF  CYANIDE  PRACTICE 

Dissolving  Effect  of  Alkalis  upon  Metals.  —  Alkalis  have  an 
important  influence  in  cyaniding,  through  their  tendency  to  act 
upon  the  base  metals  to  convert  them  into  oxides  and  hydrates. 
This  action  is  noticeable  in  connection  with  nearly  all  the  base 
metals.  By  altering  the  metals  into  the  softer  oxides  and  hy- 
droxides, and  by  decomposing  and  breaking  down  and  altering 
the  compounds,  it  causes  a  greater  action  in  many  cases  —  in 
those  in  which  it  does  not  act  to  produce,  or  to  the  extent  of  pro- 
ducing inert  salts  and  oxides  —  between  the  substance  and  the 
cyanide.  By  breaking  down  the  compounds  it  better  liberates 
for  easy  dissolution  the  precious  metals  that  they  have  chemically 
and  mechanically  imprisoned.  These  effects  are  to  a  large  ex- 
tent undesirable  in  treating  gold  ores,  since  gold  is  invariably 
in  a  native  or  metallic  form  and  any  increased  liberation  of  gold 
—  which  would  be  from  the  sulphides  in  most  cases  —  would 
be  overcome  by  the  deleterious  effects  of  the  greater  reactions 
between  the  base  metals  or  compounds  and  the  cyanide,  the 
mechanical  liberation  by  fine-grinding  being  preferable.  With 
silver  ores  this  effect  is  in  many  cases  highly  desirable,  for  silver 
is  generally  both  chemically  combined  and  mechanically  alloyed 
or  held  with  other  substances.  The  effect  of  high  protective 
alkalinity  in  treating  gold  ores  is  to  lessen  the  extraction  and 
increase  the  time  of  dissolution.  High  alkalinity  or  lime  de- 
creases the  solubility  of  both  native  gold  and  silver  in  cyanide 
solutions,  and  where  sulphides  and  base  metal  compounds  are 
found,  will  cause  more  alkaline  sulphides  to  form  in  the  solution 
(see  Alkaline  Sulphides  and  Sulphocyanides)  and  the  base 
metals  to  be  more  acted  upon.  For  this  reason  a  high  protective 
alkalinity  when  treating  sulphide  gold  ores  is  especially  unde- 
sirable, but  of  value  in  the  working  of  sulphide  silver  ores  in 
which  the  silver  and  sulphur  are  chemically  combined.  Cases 
have  been  noted  in  working  sulphide  gold  ores  where  solutions 
slightly  "  acid,"  showing  no  protective  alkalinity,  have  given 
a  higher  extraction  than  those  having  a  protective  alkalinity, 
though  at  the  expense  of  an  increased  cyanide  consumption. 

Amount  of  Lime  or  Protective  Alkalinity  Required.  —  The 
amount  of  lime  or  protective  alkalinity  used  will  vary  with  the 
material  treated,  the  method  of  cyanidation  used,  and  the  ideas 
of  the  metallurgist  in  charge.  Even  the  metallurgist  may  vary 
the  amount  greatly,  as  the  result  of  careful  study  of  the  plant 


ALKALINITY  AND  LIME  61 

practice  and  laboratory  experiments.  Where  it  is  necessary  to 
assist  the  settling  of  the  slime  by  using  lime,  the  results  when 
using  varying  quantities  are  noted,  and  that  amount  used  which 
will  give  good  settling  results  with  a  reasonable  quantity.  The 
amount  used  for  neutralizing  purposes  depends  upon  the  nature 
of  the  ore,  and  indirectly  upon  how  the  lime  is  applied.  In  the 
treatment  of  gold  ores  it  is  aimed  to  have  only  a  slight  protective 
alkalinity.  It  will  be  attempted  in  the  average  gold  plant  to  keep 
the  protective  alkalinity  of  the  solutions  at  some  standard  be- 
tween .005  per  cent  (.1  pound)  and  .025  per  cent  (.5  pound) 
lime  (CaO).  Except  where  necessary  for  settling  purposes,  solu- 
tions containing  an  average  protective  alkalinity  of  more  than 
.04  per  cent  (.8  pound)  CaO  will  seldom  be  found  in  gold  plants. 
On  the  other  hand,  in  the  treatment  of  silver  ores  a  high  pro- 
tective alkalinity  is  generally  used,  ranging  from  .025  per  cent 
(.5  pound)  to  a  maximum  or  saturated  solution  of  lime,  .125 
per  cent  (2.5  pounds),  and  even  a  little  higher  where  the  pulp 
or  solution  contains  other  alkaline  constituents.  Some  plants 
treating  silver  ores  use  that  protective  alkalinity  in  the  solution 
or  that  quantity  of  lime  which  will  cause  the  mill  solution  titra- 
tions  for  free  cyanide  and  total  cyanide  to  approximately  coincide, 
—  usually  a  case  of  a  protective  alkalinity  of  about  .1  per  cent 
(2  pounds)  CaO  —  the  principle  and  some  discussion  of  which 
has  been  given  under  Total  Cyanide.  Plants  treating  gold  ores 
will  usually  use  from  1  to  5  pounds  CaO  per  ton  of  ore  treated, 
and  silver  plants  from  3  to  10  pounds,  though  as  high  as  20 
pounds  are  being  used. 

Methods  of  Adding  Lime.  —  The  lime  is  added  in  cyanide 
practice  in  various  ways.  It  may  be  added  dry  to  the  ore  in  the 
bins,  or  fed  dry  or  wet  as  a  milk  of  lime  into  the  crushing  and 
grinding  machines.  Feeding  the  lime  into  the  fine-crushing 
machinery  is  an  excellent  method  when  crushing  in  solution  or 
when  the  mill  water  is  circulated  for  reuse,  as  it  allows  early 
action  upon  the  cyanicides  of  the  ore,  and  yet  there  is  no  mechani- 
cal loss.  When  used  in  this  way,  the  pipes  returning  the  water 
or  solution  for  reuse  in  crushing  should  be  large  and  easily  taken 
down,  for  they  may  be  gradually  lined  with  a  deposit  of  lime  and 
alumina  salts  that  must  be  periodically  removed.  These  pipes 
have  sometimes  been  replaced  with  open  wood  troughs.  Lime 
often  causes  trouble  by  coating  the  mill  screens  and  blinding 


62  TEXT  BOOK  OF  CYANIDE  PRACTICE 

their  openings,  especially  with  woven-wire  screens.  A  change 
to  the  punched  or  slotted-plate  type  may  remedy  the  difficulty. 
Lime  has  in  some  cases  given  trouble  on  the  amalgamating 
plates,  but  this  can  usually  be  overcome,  especially  if  a  thick 
bed  of  amalgam,  free  from  substances  that  the  alkali  may  alter, 
is  kept  on  the  plates. 

A  favorite  method  of  adding  the  lime  is  after  the  crushing,  but 
just  before  the  pulp  reaches  the  cyanide  tanks,  supplying  the 
lime  freshly  wet-crushed  from  a  single-stamp  battery  or  grinding 
pan  fed  by  an  automatic  feeder;  or  from  a  small  tank  fitted  with 
agitator  blade,  ascending  current  of  water,  or  other  method  of 
agitation,  into  which  lime  is  dumped  at  intervals.  Lime  is 
sometimes  added  in  unslacked  form  directly  to  an  agitation 
charge,  but  should  first  be  slacked  and  then  added  as  a  milk  of 
lime.  When  leaching  vats  are  filled  with  dry  ore,  the  lime  is 
distributed,  invariably  slacked  in  a  dry,  powdery  form,  in  small 
lots  to  be  well  mixed  with  the  charge;  this  is  the  most  effective 
way  of  adding  lime.  Where  the  sand  vats  are  filled  with  wet, 
flowing  pulp,  the  necessary  lime  is  usually  added  crushed  wet 
into  the  pulp  stream  as  stated  before.  Much  of  the  finer  and  the 
quickly-dissolved  portion  of  the  lime  overflows  the  vat  and  is  lost, 
unless  the  mill  water  is  reused  or  crushing  in  solution  is  practiced. 
Small  quantities  may  be  added  by  the  inconvenient  method  of 
sprinkling  it  over  the  top  of  the  charge  and  raking  it  in.  A 
method  which  can  be  resorted  to  is  to  add  the  lime  to  the  stock 
solution  tanks,  thus  making  the  cyanide  solution  a  strongly 
saturated  solution  of  lime  water.  This  method  is  open  to 
criticism  as  temporarily  giving  an  inordinately  high  protective 
alkalinity  where  a  constant  low  one  is  desired.  Yet  on  ore  con- 
taining many  cyanicides,  a  solution  low  in  cyanide  and  strong 
in  alkalinity  is  often  used  first  on  a  leaching  charge,  that  the 
cyanicides  may  be  cheaply  neutralized  before  adding  the  stronger 
cyanide  solution. 

The  method  of  adding  the  lime  deserves  careful  consideration. 
If  milk  of  lime  is  added  to  the  pulp  flowing  to  leaching  vats,  the 
overflow  of  which  runs  to  waste,  much  of  the  lime  will  be  lost. 
If  added  in  granules,  they  will  sink  with  the  grains  of  pulp, 
become  imbedded  in  the  charge,  and  gradually  dissolve  and 
give  off  their  alkali,  thus  doing  effective  work.  The  size  of  the 
granules  of  lime  required  will  vary  with  the  nature  of  the  ore  and 


ALKALINITY  AND  LIME  63 

its  treatment.  They  should  be  of  such  size  that  the  lime  will 
dissolve  and  give  off  its  neutralizing  power  as  fast  as  needed. 
This  will  be  indicated  by  the  solution  issuing  from  the  vat.  It 
should  at  all  times  have  a  small  protective  alkalinity,  but  at  no 
time  an  inordinately  high  amount,  yet  on  the  principle  of  economy 
the  lime  should  be  all  dissolved  and  used  by  the  time  the  treat- 
ment is  finished.  The  cyanicides  of  some  ores  show  themselves 
very  fully  at  the  start,  others,  especially  heavily  sulphuretted 
ores,  gradually  undergo  oxidation  and  develop  cyanicides  and 
alkali  and  cyanide-consuming  compounds  during  the  whole  time 
of  their  treatment.  Consequently,  each  case  is  a  separate  problem 
of  both  how  to  add  the  lime  to  the  best  advantage  in  view  of 
its  influence  on  the  dissolution  and  precipitation  of  the  precious 
metals  and  the  consumption  of  cyanide,  and  how  to  get  the 
maximum  efficiency  of  the  lime.  Between  adding  lime  in  un- 
slacked  coarse  granules  and  as  a  milk  of  lime  is  a  wide  variation. 

Lime  v.  Caustic  Soda.  —  Caustic  soda  (NaOH)  was  at  one  time 
used  extensively  for  neutralizing  purposes,  but  lime  was  generally 
found  to  be  superior  as  the  salts  or  compounds  of  lime  —  mainly 
calcium  sulphate  —  are  very  insoluble,  while  those  of  caustic  soda 
are  extremely  soluble.  In  this  way  the  lime  salts  are  precipitated 
in  the  ore  where  formed  instead  of  entering  the  solution,  where 
they  may  exert  some  influence  and  perhaps  be  precipitated  in  the 
zinc  boxes  as  sometimes  occurs  in  using  caustic  soda.  The  exces- 
sive use  of  caustic  soda  as  a  neutralizer  will  cause  trouble  with  the 
zinc  precipitation  much  quicker  than  the  use  of  lime.  One  ad- 
vantage of  caustic  soda  —  when  such  an  advantage  is  desired  — 
is  its  extreme  solubility;  it  will  dissolve  in  an  equal  weight  of 
water,  while  1  part  of  CaO  requires  800  parts  of  water.  Pure 
lime  has  1.43  times  the  neutralizing  strength  of  caustic  soda  and 
is  much  cheaper. 

Determination  of  Causticity  of  Lime,  etc.  —  Commercial  lime 
is  always  more  or  less  impure,  containing  varying  amounts  of 
sand,  clay,  iron,  carbon,  etc.  These  were  contained  in  the  origi- 
nal limestone  or  are  due  to  the  fuel.  The  available  or  useful 
alkali  may  be  roughly  estimated  by  taking  a  weighed  and  pow- 
dered sample  of  the  unslacked  lime,  mixing  it  with  water  to  form 
a  very  dilute  and  liquid  emulsion  containing  a  definite  per  cent 
of  the  commercial' CaO,  and  titrating  it,  as  in  the  test  for  pro- 
tective alkalinity.  The  comparative  efficiency  of  the  lime  when 


64  TEXT  BOOK  OF  CYANIDE  PRACTICE 

dissolved  or  slacked  in  cold  water  and  in  hot  water  should  be 
tested  by  titrating  a  similar  lime-test  solution  that  has  been 
boiled,  for  grinding  or  thoroughly  disintegrating  the  lime  in  hot 
water  will  usually  give  a  higher  alkalinity.  For  more  accurately 
obtaining  the  causticity  or  available  CaO  or  alkali,  weigh  out  2 
grams  of  the  powdered  unslacked  lime,  make  up  to  1000  c.c.  with 
water  and  20  grams  of  pure  cane  sugar,  shake  at  intervals  over  a 
period  of  12  hours,  and  finally  remove  an  aliquot  part  and  titrate 
with  the  decinormal  acid  and  phenolthalein. 

If  it  is  feared  that  the  lime  contains  reducing  agents  that  will 
destroy  the  cyanide,  a  clean,  hew,  cyanide  solution  should  be  made 
up  for  test  purposes,  titrated  for  its  strength,  and  lime  added  in 
varying  quantities  with  titrations  to  determine  if  the  cyanide 
strength  is  reduced.  Lime  sometimes  gives  trouble  by  the  car- 
bon and  carbonaceous  matter  in  it  or  introduced  in  the  burning- 
process,  precipitating  the  gold  and  silver.  Agitating  lime  with 
metal-bearing  solution,  either  in  the  laboratory  or  in  the  gold 
stock  tanks,  with  assays  of  the  solution  before  and  after,  will 
indicate  regarding  this. 


CHAPTER  VII 
ORE   TESTING   AND   PHYSICAL   DETERMINATIONS 

IN  making  laboratory  tests  on  ore  for  the  extraction  of  its  gold 
and  silver  by  cyanide,  the  principles  governing  and  the  points 
arising  in  the  actual  working  of  the  ore  must  be  borne  in  mind, 
rather  than  an  attempt  to  imitate  the  -exact  details  of  plant 
practice.  The  experienced  cyanide  operator  in  making  tests  on 
ore,  while  employing  careful  laboratory  methods,  observation, 
and  study,  visualizes  the  sample  of  a  few  pounds  into  a  full-sized 
working  charge,  correlating  each  detail  occurring  in  the  sample 
to  that  which  would  take  place  in  a  working  charge. 

Facts  to  be  Determined.  —  The  principal  things  to  be  ascer- 
tained or  to  be  examined  into  are:  nature  and  composition  of 
the  ore;  nature  of  the  metal  and  the  condition  in  which  it  is 
held  in  the  ore;  special  treatment  which  may  be  necessary,  as 
roasting,  water-washing,  aeration,  removal  of  cyanicides,  amal- 
gamation, concentration,  etc.;  amount  of  lime  or  other  neutral- 
izer  required;  strength  of  cyanide  to  be  used,  with  probable 
quantity  required,  and  consumption  that  will  take  place;  time 
required  for  dissolving  the  gold  and  silver;  fineness  of  crushing 
required  for  an  economically  high  extraction,  and  the  variation 
due  to  crushing  to  varying  degrees  of  fineness,  including  the 
results  of  sizing  tests  showing  the  amount  of  different  mesh 
material  produced,  and  the  value  of  each  before  and  after  treat- 
ment; tendency  of  ore  to  slime,  and  quick  or  slow  settling  effect; 
also  how  it  will  percolate. 

Methods  of  Testing.  —  To  work  these  tests  out  fully  requires 
a  great  amount  of  labor  and  time.  It  is  customary  to  start  with 
small  bottle  tests  of  perhaps  a  few  ounces  or  pounds,  and  after 
the  characteristics  of  the  ore  have  been  learned  to  increase  to 
25  to  100-pound  lots;  and  finally,  especially  if  the  ore  is  a  silver 
one  or  shows  any  refractory  tendencies,  to  test  at  a  custom  test- 
ing plant  or  in  a  small  experimental  plant  at  the  rate  of  500  pounds 

65 


66  TEXT  BOOK  OF  CYANIDE  PRACTICE 

or  a  few  tons  per  charge.  Tests  in  bottles  are  easily  made  and 
will  quickly  exhibit  to  the  experienced  operator  the  lines  along 
which  the  metallurgical  system  is  to  be  developed.  They  are 
insufficient  to  build  a  plant  on,  even  presuming  that  the  same 
dissolution  would  be  effected  in  the  plant  as  in  the  preliminary 
tests,  for  cyanide  and  crushing  plants  and  processes  are  not  fully 
standard  to  all  classes  of  material,  and  consequently  should  be 
designed  to  meet  the  necessities  of  the  ore,  which  must  be  learned 
by  extended  experimental  work. 

Securing  Samples.  —  The  first,  and  probably  the  hardest 
thing,  unless  under  the  direction  of  an  experienced  man  alive  to 
the  dangers,  is  to  get  proper  samples  of  the  ore.  The  tendency 
is  to  take  samples  that  are  too  well  oxidized,  for  the  ore  promi- 
nently exposed  during  the  early  days  of  a  mine  is  the  oxidized 
ore  near  the  surface.  Often  the  samples  are  taken  from  dumps 
that  have  long  weathered.  Tests  on  this  nature  of  ore  will 
invariably  indicate  a  high  extraction  with  coarse  crushing  and 
either  without  or  with  but  little  concentration.  Whereas,  when 
the  harder,  unoxidized,  baser  ores  are  worked,  there  is  a  lower 
extraction  obtained,  a  finer  crushing  required,  and  after  a  lapse 
of  considerable  time  the  operators  awake  to  the  fact  that  con- 
centration or  closer  concentration  by  a  more  elaborate  concen- 
trating plant,  or  changes  to  give  greater  attention  to  the  sulphide 
content  of  the  ore,  will  increase  the  profits  to  a  large  extent.  In 
some  cases  the  samples  represent  too  fine  a  material,  in  others 
too  coarse.  This  may  result  in  increasing  or  decreasing  the  appar- 
ent value  of  the  material  to  be  treated  or  the  amount  of  some 
constituent  in  it,  or,  by  giving  undue  proportions  between  the 
slime  and  sand,  may  cause  the  installation  of  an  unsuitable 
system.  When  the  mine  contains  different  classes  of  ore,  as 
oxidized  and  unoxidized,  clean  "  free  milling  "  and  base,  high 
and  low  grade,  those  that  slime  and  those  that  are  hard  and 
dense,  and  separate  shoots  or  ledges  containing  copper,  zinc, 
lead,  etc.,  each  class  should  be  tested  separately  and  not  averaged 
together.  This  distinction  should  be  borne  in  mind  after  the 
plant  is  in  operation,  for  a  plant  using  cyanidation  may,  like  a 
smelter,  find  it  desirable  to  mix  certain  ores  in  some  cases  and 
keep  them  separate  in  others,  to  get  a  certain  proportion  of  sand 
and  slime,  or  to  treat  an  easily  worked  ore  differently  from  a 
refractory  one. 


ORE  TESTING  AND  PHYSICAL  DETERMINATIONS    67 

Physical  Examination  of  Ores.  —  The  ore  to  be  tested  should 
first  be  closely  examined  and  studied,  for  its  characteristics, 
conditions  under  which  it  is  found,  the  methods  employed  upon 
similar  ore  in  the  same  or  other  districts,  and  the  results  from 
assays,  pannings,  microscopical  examination,  etc.,  will  indicate 
the  nature  of  treatment  that  will  probably  be  required.  If  it  is 
a  soft,  porous  ore  which  a  solution  can  easily  penetrate,  coarse 
crushing  such  as  is  done  in  a  dry-crushing  mill  may  be  sufficient. 
If  it  is  a  hard,  dense  ore  which  the  solution  cannot  penetrate,  fine 
crushing  will  be  required  to  liberate  the  metal  to  the  solvent 
action  of  the  cyanide.  The  metal  may  lie  on  the  breaking  or 
parting  planes  of  the  ore  or  on  the  faces  of  the  crystals,  in  which 
case  extremely  fine  crushing  will  not  be  required  to  expose  it; 
whereas  when  it  is  embedded  in  the  crystals  or  sulphide,  very 
fine  crushing  is  required.  Where  the  metal  is  in  coarse  grains, 
it  must  be  removed  by  amalgamation  or  careful  concentration, 
or  a  long  contact  with  a  strong  solution  will  be  required  to  dis- 
solve it,  unless  it  is  ground  into  small  particles  or  thin  scales  by 
a  tube  mill  or  other  slimer.  Where  the  metal^  is  in  an  extremely 
fine  state  of  division  or  in  very  thin  scales,  a  low  strength  of 
solution  will  dissolve  it  quickly.  If  the  ore  contains  limonite, 
kaolin,  alunite,  talc,  etc.,  that  becomes  a  colloidal,  slow-settling, 
and  unmanageable  slime,  only  the  leaf  filter  can  handle  it  to  an 
advantage.  Where  the  ore  contains  sulphides,  it  becomes  a 
question  whether  to  remove  them  or  not  before  cyanidation. 
It  is  customary  to  remove  them  by  concentration  when  they 
represent  a  considerable  proportion  of  the  value,  or  introduce 
interfering  substances  into  the  ore.  A  sulphide  or  base  ore  will 
generally  necessitate  finer  grinding  to  liberate  the  metal.  Tel- 
luride  ore  is  invariably  treated  by  roasting  or  bromocyanide. 
Ore  containing  copper  may  require  the  removal  of  the  copper  by 
concentration  or  by  leaching  with  very  dilute  sulphuric  acid  be- 
fore applying  the  cyanide,  while  other  copper  ores  may  be  suc- 
cessfully worked  by  using  low-strength  solutions  that  will  act  less 
strongly  upon  the  copper.  Ores  containing  antimony,  and  to  a 
less  extent  manganese  or  arsenic,  may  give  low  extractions  and 
require  aeration,  etc.  Sulphide  ore  may  require  considerable 
aeration.  Clean  and  unoxidized  ore  will  require  little  lime  or 
other  neutralizer  of  the  acidity,  while  oxidized  and  base  ore  will 
require  a  large  amount. 


68  TEXT  BOOK  OF  CYANIDE  PRACTICE 

Free  Acidity.  —  The  first  test  that  may  be  made  is  for  free 
acidity  or  that  which  is  soluble  and  can  be  washed  out  of  the  ore. 
Take  20  grams  or  more  of  ore  ground  to  the  mesh  expected  to  be 
used.  Add  the  same  number  of  cubic  centimeters  of  water  and 
agitate  for  ten  minutes  or  longer.  Filter  dnd  titrate  10  c.c.  of 
the  filtrate  with  decinormal  caustic  soda  solution  until  the  solu- 
tion becomes  alkaline  as  described  under  the  test  for  hydro- 
cyanic acid  and  protective  alkalinity.  This  will  give  the  number 
of  pounds  of  caustic  soda  or  lime  required  to  neutralize  the 
soluble  acidity  in  one  ton  of  water,  and  if  the  same  weight  of  water 
as  of  ore  was  taken,  the  results  indicate  the  caustic  soda  or  lime 
required  per  ton  of  ore  to  neutralize  the  free  or  soluble  acidity. 

Latent  Acidity.  —  Latent  acidity,  or  that  which  is  insoluble, 
is  determined  by  washing  a  weighed  sample  or  that  used  in  de- 
termining the  free  acidity  until  the  washings  show  no  acidity, 
then  adding  some  water  to  the  ore  and  the  alkaline  indicator, 
and  titrating  with  the  decinormal  alkali  solution  until  the  ore 
solution  becomes  alkaline.  The  results  are  figured  in  the  same 
way  as  for  free  acidity,  except  that  the  titration  is  computed 
for  the  number  of  grams  of  ore  used.  A  method  giving  higher 
and  more  correct  results  consists  of  diluting  with  the  necessary 
amount  of  water  and  adding  standard  caustic  soda  solution  in 
some  excess  of  that  required  to  make  alkaline,  agitating  for 
half  an  hour  or  longer,  filtering  and  washing  ore  until  no  more 
alkalinity,  then  titrating  to  neutrality  by  standard  acid.  As  a 
standard  acid  and  alkali  exactly  equal  each  other,  the  difference 
between  the  alkali  added  and  the  acid  required  to  neutralize  the 
excess,  will  give  the  latent  acidity. 

Total  Acidity.  —  The  total  acidity,  that  due  to  both  the  free 
and  latent,  which  is  what  is  usually  required,  is  found  as  for 
latent  acidity  without  first  water-washing.  Where  the  ore  to  be 
tested  is  wet,  it  should  not  be  dried,  for  more  acidity  will  be  gen- 
erated from  the  iron,  pyrites,  etc.;  but  the  tests  should  be  made 
first,  after  which  the  ore  is  dried  and  weighed  for  calculating  the 
results. 

These  tests  for  acidity  will  indicate  with  little  accuracy  con- 
cerning the  amount  of  lime  required,  for  more  will  be  used  in 
practice,  owing  to  the  large  proportion  of  impurities  in  the  lime,  — 
which  should  always  be  borne  in  mind,  —  to  the  lime  not  dissolved 
or  uneconomically  used,  and  to  further  acidity  which  may  be 


ORE  TESTING  AND  PHYSICAL  DETERMINATIONS    69 

generated.  A  closer  approximation  of  the  amount  can  be  ob- 
tained through  tests  made  by  the  use  of  bottles,  introducing 
20  grams  or  more  of  ore  into  each,  together  with  the  same  num- 
ber of  cubic  centimeters  of  a  fresh  cyanide  solution  of  .working 
strength  and  varying  weighed  quantities  of  lime,  as  .05  (1  pound 
per  ton  of  ore),  .15  (3  pounds),  or  .25  per  cent  (5  pounds)  or  more 
of  the  weight  of  ore,  agitating  for  3p  minutes  or  lonjger,  filtering 
and  testing  10  c.c.  of  each  for  cyanide  consumption  and  pro- 
tective alkalinity.  That  solution  which  indicates  a  protective 
alkalinity  below  .3  per  cent  (.6  pound)  CaO  will  probably  show 
a  low  consumption  of  cyanide,  and  indicates  the  amount  of  lime 
to  be  used  on  clean  ores,  though  as  the  ore  becomes  baser  the 
lime  and  cyanide  consumption  cannot  be  estimated  from  such 
short  contacts  or  so  generally  — -  the  actual  practice  must  be 
imitated. 

Extraction  Tests  with  Bottles.  —  The  most  important  thing 
in  all  cyanide  tests  is  to  learn  the  highest  dissolution  of  gold  and 
silver  that  can  be  effected.  Bottle  tests  on  gold  ores  will  usually 
give  this  as  closely  as  a  working  charge  of  several  hundred  tons, 
if  the  sample  is  representative,  in  the  same  way  as  a  small  por- 
tion taken  for  assay  represents  a  carload  or  a  day's  run  of  ore. 
As  the  ore  becomes  baser  and  with  silver  ores,  bottle  tests  cannot 
be  relied  upon  so  strongly,  for  on  account  of  the  comparatively 
slow  dissolution  of  the  precious  metals  in  such  ores  the  maximum 
dissolution  may  not  be  effected.  Bottle  tests,  besides  giving  the 
maximum  extraction,  indicate  less  accurately  the  strength  of 
cyanide  to  be  used,  the  consumption  that  will  take  place,  the 
time  required  for  dissolution,  and  the  amount  of  lime  to  be  used; 
also,  by  testing  the  solution,  the  nature  of  the  cyanicides. 

For  making  simple  bottle  tests  on  gold  ores,  take  wide-mouthed 
bottles  and  introduce  into  each  2  assay  tons  of  ore  ground  to  the 
mesh  expected  to  be  necessary,  together  with  the  amount  of 
lime  or  neutralizer  that  the  bottle  test  before  described  shows 
to  be  necessary  to  give  a  small  protective  alkalinity.  In  the 
absence  of  having  made  this  test,  use  an  amount  in  excess  of  that 
indicated  by  the  test  for  total  acidity.  Add  120  c.c.  of  a  new 
cyanide  solution  to  each  bottle,  making  the  first  .  1  per  cent  (2 
pounds)  KCN,  the  second  .175  per  cent  (3.5  pounds)  KCN,  and 
the  third  .25  per  cent  (5  pounds)  KCN.  If  it  is  a  clean  ore  con- 
taining the  gold  in  a  finely-divided  state,  a  charge  should  be  tried 


70  TEXT  BOOK  OF  CYANIDE  PRACTICE 

using  a  strength  of  .05  per  cent  (1  pound)  KCN.  With  a  base 
gold  or  an  easily-worked  silver  ore  a  charge  of  .375  per  cent 
(7.5  pounds)  KCN  should  be  tried,  while  with  a  base  silver 
ore  or  a  very  base  gold  ore,  the  test  should  be  made  with  solutions 
from  .1  per  cent  (2  pounds)  to  .6  per  cent  (12  pounds).  These 
bottles  should  be  agitated  for  24  hours,  or  left  stand  with  occa- 
sional shakings  for  48  to  72  hours.  If  the  ore  contains  the  gold 
in  a  finely-divided  state  and  little  sulphide,  the  value  will  be 
dissolved  within  12  hours.  If  the  ore  is  very  base,  it  may  require 
more  than  72  hours'  contact,  unless  continuous  agitation  is  given. 
Some  silver  ores  may  require  a  few  days'  continuous  agitation 
or  contact  for  a  week  with  strong  solution.  The  bottles  should 
be  uncorked  at  times  to  aerate.  At  the  end  of  the  period,  filter 
each  charge  and  test  for  cyanide  consumption  and  protective 
alkalinity,  which  can  be  reduced  to  tons  of  ore,  since  each  assay 
ton  of  ore  was  treated  with  approximately  2  assay  tons  of 
solution.  Wash  the  ore  by  decantation  or  on  a  filter  for  some 
time  after  all  alkalinity  is  removed,  —  a  thorough  washing  is 
most  essential.  Finally  dry  and  assay.  At  the  same  time  as 
making  these  tests  it  would  be  well  to  grind  a  sample  of  the  pulp 
to  200-mesh  and  treat  it  with  a  strong  solution  (.375  to  .5  per 
cent  —  7.5  to  10  pounds  —  KCN)  with  a  few  decantations  and 
additions  of  new  solutions,  that  the  results  of  the  residue  assay 
may  be  taken  as  the  maximum  extraction  under  ideal  conditions 
for  comparison  with  the  regular  bottle  tests.  With  silver  ores 
and  sulphides,  lead  acetate  at  the  rate  of  1  pound  per  ton  of  ore 
should  be  added  to  the  charge  or  solution  to  remove  any  alkaline 
sulphides  formed.  If  the  ore  reaches  the  cyanide  plant  wet  and 
without  drying,  it  should  be  treated  that  way  in  the  test,  for  a  pre- 
liminary drying  would  oxidize  the  ore  and  probably  give  a  higher 
extraction  than  the  plant  could  in  actual  practice.  The  differ- 
ence between  the  assays  of  the  sample  before  and  after  treatment 
gives  the  extraction;  this  may  be  checked  by  drawing  off  30  c.c. 
or  any  aliquot  part  of  the  solution  and  assaying.  Or  the  effect 
of  further  contact  with  the  solution  may  be  tested  by  drawing 
off  or  removing  the  aliquot  portion  of  the  solution  and  assaying 
the  same,  followed  by  retreating  the  ore  with  fresh  solution 
before  washing  and  drying  it  for  assay.  The  bottles  may  be 
continuously  agitated  by  being  attached  to  some  suitable  moving 
device,  as  a  wheel,  in  which  case  the  extraction  will  take  place 


ORE  TESTING  AND  PHYSICAL  DETERMINATIONS    71 

quickly,  just  as  agitation  in  actual  practice  causes  the  value  to 
go  into  solution  in  a  comparatively  short  period. 

Agitation  tests  with  lots  of  2  or  3  pounds  of  ore  may  be  con- 
veniently made  in  large  acid  bottles.  The  amount  of  solution 
used  should  be  from  two  to  four  times  that  of  the  dry  ore  by 
weight,  or  even  more.  An  air-agitating  tank  may  be  constructed 
in  various  ways,  such  as  by  cutting  off  the  bottom  of  a  large 
wine  or  other  bottle  having  a  long,  sloping  neck.  This  is  placed 
in  an  upright  position  with  neck  down.  A  f-inch  glass  tube  is 
suitably  supported  from  near  the  bottom  of  the  neck  to  within 
2  inches  of  the  top.  Through  the  cork  in  the  neck  of  the  bottle 
passes  a  J  or  J-inch  glass  tube  delivering  air  into  the  bottom  of 
the  f-inch  glass  tube.  A  charge  sufficient  to  nearly  submerge  the 
central  tube  is  placed  in  the  agitator  and  a  slight  amount  of  air 
turned  on,  resulting  in  circulating  the  pulp  up  the  central  tube 
and  down  the  outside  of  it.  Any  modification  of  this  —  the 
Pachuca  air-lift  tank  principle  —  may  be  used. 

In  agitation  tests,  samples  should  be  taken  hourly  or  every  few 
hours  by  means  of  a  tube,  preferably  of  glass,  inserted  to  the 
bottom  of  the  charge,  the  upper  end  closed  with  the  finger  and 
quickly  withdrawn,  or  some  of  the  pulp  may  be  syphoned  off. 
Care  must  be  exercised  to  get  a  true  sample  of  the  pulp  and  not 
one  containing  too  little  of  the  coarser  material,  nor  should  the 
amount  removed  be  sufficient  to  vitiate  the  final  sample.  The 
sample  should  be  tested  for  cyanide  strength,  protective  alkalinity, 
and  gold  and  silver.  If  the  consumption  of  cyanide  or  alkalinity 
is  large,  it  may  be  necessary  to  add  more  during  the  agitation. 

Percolation  Tests.  —  Percolation  tests  more  closely  imitate 
leaching  practice  and  consequently  are  often  used.  These  are 
made  in  glass  percolators  or  by  using  large  acid  or  smaller  bottles 
as  such  by  cutting  their  bottoms  off,  the  discharge  of  the  per- 
colator being  fitted  with  a  rubber  tube  and  a  pinchcock.  A 
filter  bottom  of  muslin  or  light  canvas  is  arranged  on  a  platform 
in  the  bottom  of  the  percolator,  after  which  the  charge  of  Ore 
containing  the  proper  amount  of  neutralizer  is  added;  this  may 
be  as  small  as  2  pounds  if  crushed  medium  fine.  There  is  set 
above  the  percolator  a  vessel  containing  the  cyanide  solution  to 
be  used,  which  may  be  drawn  off  by  a  small  cock  or  syphoned 
out  by  a  rubber  tube,  the  stream  of  which  is  regulated  by  a  pinch- 
cock.  If  it  is  desired  to  measure  the  solution,  an  amount  by 


72  TEXT  BOOK  OF  CYANIDE  PRACTICE 

weight  equal  to  twice  the  amount  of  ore  is  convenient.  Thus 
if  600  grams  of  ore  have  been  taken,  1200  c.c.  of  solution  may  be 
used.  The  ore  in  the  percolator  is  covered  with  this  solution, 
after  which  the  discharge  cock  is  opened  to  allow  a  drip  sufficient 
to  drain  the  entire  amount  of  solution  through  the  charge  in  the 
allotted  time,  which  is  usually  three  days  with  simple  gold  ores, 
and  longer  with  very  base  and  silver  ores.  The  solution  in  the 
reservoir  being  allowed  to  drip  into  the  percolator  at  a  rate 
sufficient  to  keep  the  charge  covered.  Occasionally  the  entering 
drip  should  be  shut  off  to  allow  the  charge  to  drain  and  to  aerate 
for  a  short  time,  after  which  the  charge  should  be  covered  with 
solution  and  percolation  started.  After  final  percolation  and 
drainage,  the  charge  should  be  thoroughly  washed  past  the 
point  where  the  washings  show  not  even  a  trace  of  alkalinity, 
when  it  is  dried  and  assayed.  The  solutions  and  washings  are 
saved,  measured,  titrated  for  cyanide  strength  and  protective 
alkalinity,  assayed  for  gold  and  silver,  and  the  results  figured 
out.  By  using  a  good  sized  charge  and  sampling  at  regular 
periods  when  drained  by  a  sampler  resembling  a  cheese  drier,  by 
plunging  a  tube  into  the  charge,  or  by  removing  the  charge,  the 
progress  of  the  dissolution  of  gold  and  silver  can  be  noted.  These 
samples  must  be  well  washed  without  any  delay.  By  running 
several  percolation  tests  together  on  parts  of  the  same  sample, 
using  different  strengths  of  solution  and  sampling  at  regular 
intervals,  the  necessary  data  regarding  strength  of  solution  to  be 
used,  consumption  of  cyanide,  and  time  required  for  dissolution 
can  be  learned,  but  not  the  degree  of  fineness  to  which  the  ore 
should  be  crushed. 

Fineness  of  Ore  Required.  —  To  learn  the  degree  of  fineness 
to  which  the  ore  should  be  crushed,  the  simplest  forms  of  bottle 
tests  that  use  a  solution  sufficiently  strong  and  a  long  enough 
application  to  get  the  maximum  extraction  is  all  that  is  required. 
The  ore  should  be  crushed  and  ground  to  those  of  the  following 
sizes  which  may  be  deemed  necessary,  4,  10,  20,  30,  60,  100,  150, 
and  over  200-mesh.  The 'results  of  cyaniding  those  sizes  that 
give  a  good  extraction  should  be  shown  in  a  comparative  way  by 
plotting,  etc.,  and  studied,  for  that  degree  of  fineness  which  gives 
the  highest  extraction  may  yield  less  profit  than  when  crushing 
to  a  coarser  size,  on  account  of  the  increased  cost  of  crushing  finer 
and  cyaniding  the  finer  material. 


ORE  TESTING  AND  PHYSICAL  DETERMINATIONS    73 

Sizing  Tests.  —  The  last  xtests  to  be  made  are  sizing  tests. 
These  occupy  some  time  and  are  usually  not  made  until  the  pre- 
liminary tests  are  well  worked  out,  though  it  is  an  advantage  to 
make  them  at  all  times.  A  sample  of  the  crushed  ore  to  be 
tested  by  cyanide  amounting  to  about  2  pounds  is  taken  and 
weighed.  It  is  first  concentrated  and  reconcentrated  until  all 
sulphide  is  removed.  It  is  then  stirred  up  with  the  water  used 
in  concentrating  and  the  muddy  water  poured  off,  care  being 
exercised  that  no  fine  sand  passes  off  with  the  water,  when  it  is 
again  stirred  up  with  water  and  the  muddy  water  poured  off. 
This  is  repeated  and  repeated  until  the  sand  is  washed  entirely 
free  from  slime  that  is  of  a  light,  flocculent,  feathery  nature,  that 
agglomerates  together,  makes  water  muddy,  and  does  not  readily 
settle;  while  the  slime  product  contains  no  sand  or  granular 
matter,  however  fine.  The  slime  is  allowed  to  settle,  the  water 
poured  off,  and  the  sludge  either  dried  in  a  pan  or  run  onto  a 
filter  paper  and  dried  after  draining,  when  it  is  weighed.  The 
sand  and  concentrate  are  also  dried,  after  which  they  are  sized 
through  screens.  To  divide  the  concentrate  into  two  sizes  and 
possibly  three  is  good.  The  sands  should  be  sieved  into  at  least 
four  sizes,  the  coarsest  size  containing  not  more  than  5  or  10  per 
cent  of  material  that  may  be  considered  as  a  coarse  oversize,  —  as 
that  which  failed  to  be  crushed  to  the  desired  mesh, — while  screens 
should  be  used  that  will  divide  the  remainder  about  evenly. 
Taking  the  case  of  material  crushed  in  a  mill  through  a  40-mesh 
screen,  the  sizing  test  should  produce  the  following  sizes:  a  con- 
centrate or  a  coarse  and  fine  concentrate,  a  slime,  an  oversize  of 
5  or  10  per  cent  held  on  a  40-mesh  laboratory  screen,  a  held  on 
60,  100,  and  150-mesh,  and  a  passed  150-mesh  sand;  these  sizes 
should  be  weighed,  assayed,  and  the  results  tabulated.  If  the  ore 
contains  free  gold  liberated  by  the  crushing,  this  sizing  test  is  of 
little  or  no  value  unless  the  gold  is  removed  by  amalgamation 
or  panned  out  with  the  concentrate,  preferably  removed  by 
amalgamation. 

The  remainder  of  the  sample  from  which  the  sizing  test  and 
the  head  assay  sample  were  taken  is  now  cyanided  in  the  labora- 
tory until  the  maximum  extraction  is  obtained,  which  is  best 
performed  by  introducing  the  ore  and  solution  into  a  large  acid 
bottle  and  agitating  it  intermittently  or  continuously  as  usual. 
After  the  charge  is  washed  free  of  dissolved  gold  and  silver,  it  is 


74  TEXT  BOOK  OF   CYANIDE  PRACTICE 

sized  as  before,  the  results  being  compared  with  those  of  the  ore 
before  cyaniding,  and  both  with  other  tests  in  which  the  ore  was 
crushed  finer  or  coarser.  The  sizes  obtained*  of  the  sample  be- 
fore cyaniding  may  be  assayed,  then  cyanided  separately,  and 
the  residues  assayed,  or  the  coarser  sizes  after  cyaniding  may  be 
recrushed  and  recyanided  and  the  results  observed.  The  whole 
purpose  of  sizing  tests  is  to  show  in  what  part  of  the  ore  the 
value  lies  before  and  after  cyanidation,  and  the  effect  of  coarser 
or  finer  crushing  on  the  extraction.  While  the  straight  cyanide 
tests  made  on  the  ore  as  crushed  to  different  degrees  of  fineness 
will  show  the  increase  or  decrease  in  extraction,  so  that  the  most 
economical  size  can  be  selected,  the  sizing  tests  are  necessary 
to  a  true  diagnosis  of  conditions.  To  act  without  them  is  too 
much  like  a  physician  prescribing  for  a  sick  man  without  learn- 
ing the  nature  of  the  complaint.  It  may  be  that  by  crushing 
only  the  oversize  an  increased  economical  extraction  can  be  had, 
or  all  sizes  of  the  sand  may  respond  to  finer  crushing,  or  the  sul- 
phide or  coarser  sulphide  only  may  require  finer  crushing. 
Knowing  exactly  where  the  trouble  is,  the  metallurgist  can  pro- 
vide to  meet  that  point.  When  studying  sizing  tests  or  the 
effect  of  crushing  to  different  degrees  of  fineness,  the  metallurgist 
must  consider  more  than  the  conditions  directly  affecting  cyani- 
dation.  He  must  also  consider  the  crushing  devices  at  his  dis- 
posal or  which  can  be  reasonably  installed.  To  make  a  practical 
success  he  must  bring  such  knowledge  and  study  to  bear  that  he 
can  adjust  the  conditions  necessary  to  secure  a  high  extraction  by 
cyanidation  to  those  necessary  to  obtain  a  high  tonnage  at  a 
reasonably  low  cost  from  the  crushing  machinery,  and  find  the 
economic  mean  of  the  two.  While  many  in  making  sizing  tests 
include  the  flocculent  slime  in  the  finest  sand,  the  remaining 
sands  should  always  be  washed  free  of  the  adhering  slime,  this 
slime  to  be  added  to  the  finest  size.  The  following  will  indicate 
the  method  of  tabulating  the  results. 


TESTING  AND  PHYSICAL  DETERMINATIONS    75 


OQ    *  -« 


in 


ilt 


10  (N  <N  <M  c^  co 


SO  O  O  •*  i—  "  b-  »O 
O  CO  O  C5  CO  i—  i  O 


I     -;- 


O 


s 


i—  1  T—  I  i—  1  y—  I  CO 


8 


8 


"^"^"^5 
O    V    03 

S  S  S 


S  §  i 

2  o  o 


76 


TEXT  BOOK  OF  CYANIDE  PRACTICE 


a3 

Hll 

|?Hg 

CKMCllXN        *&<X) 
COCOCOlMCOOCOt^ 

i—  I            l—  1            I—  1   (N   i-H 

8 

CK 

T3 
C 

C3 

73 

£-S«s^ 
I1JI 

§   OCOQCX)O5Tti^CO 
.3   i—  iC^T-Hr-HOi—  ICO(M 

2  ' 

T—  I 

0 

O 

§J 

H«2 

«-    03 

*l 

£  cot^oco-^^c^io 

£    (MtOOCSt^^fCO^ 

g    d  ^  ^        '                •  ,-j  0 

^11 

•          »O         10               iO 

£    lOGC^O^GCtO^ 
^   OOOOOOi-(i—  I 

IO 

g 

10 

tff^BH 

a 

to 

T—  1 

€/& 

d 

3 

1      S 

CO^OCO^^fNiO 

o^^cococai—  ico 

Is 

P» 
o 

?  a 

i—  I                                >O  xo 

3 

1—  1                        ^   ^ 

OS           lO 

JB 

1     I 

(M^OOGOOO^O 

rHrHOOCDOtl<MT-l 

rH               !>. 

00            g 

fS      o 

(M  T-<                          OI-H 

•         oT 

1  -§  I 

bo          o        "? 

§ 

c3 

^.S-5| 

Nsl 

«S^H 

00 

^   >0  10  0  <M  >0  CO  00  (M 
•Q    Ot—  (Oi—  lOOT—  IT—  I 

Q      • 

i 

'N           o         J-T 
•3           H^     .    o> 

CQ             ^     g   j> 

&  I'? 

2 

"o 
O 

§s 

h33 

§3.2 
^ 

J  ^ooS^S^^ 

^    i-i  i-i                         '  0  rH 

c3    °    '  ~ 

6  ss 

1 

O                                        10 

0 

G-  O 
1     0    «» 

2  §2 

js 

b£) 

1 

rHiQOO<NCOCO<N 
I-H  i—  i  <N  T-t  CO 

8 

"&«&     0 

a  -o 

O 
^ 

1 

>O               >O  O  ^O  1C 
t^               t^  iO  t^  (M 

8 

111 

2 
o 

OOCOrt<l>.COOaiCD 
(MOO(Mt^T—  t  r-l  i—  l 

O5 
§ 

H  cS  <J 

:  --a 

•   vi 

•    •  o 

:  .   :  :  :  :  •  g 

•SJc 

'  '  i  '  <^§ 

::::::  gS 

:  :  '  :  .'6^3 

•^^^  •   -2  g 
-S  SS  8-S   :c^ 

§  a  s  a  g  :  §  & 

i  cb  o  o  j     Ida; 
ooiooo  o"ti"t^ 

CO-H^CQO    g    g    g 

CCCfl^'-^^ 
000   OTJ-S    g   g 

2222  ^  a?  g  g 

'a'o'o'a;  ci  S  o  o 
WWWWPLHHOO 

ORE  TESTING  AND  PHYSICAL  DETERMINATIONS    77 


Comparison  of  "Head"  and  "Tail"  Sizing  Tests 
Charge  No.  76.     Jan.  10-18,  1911. 

• 

Extraction  per  Ton  Each  Size. 

Extraction 
per  Ton 
of  Ore. 

Gold 

Silver. 

Total. 

Per  cent. 

Dollars. 

Held  on  60-mesh     .  . 

Per  cent. 
60. 

33.3 
50. 
53.8 
69. 
88.9 
79.9 
87. 

Per  cent. 
45.5 

36.7 
50. 
66. 
64. 

81.7 
71.8 
78.1 

54.1 
34.6 
50. 
59.5 
67. 
86.5 
76.9 
83.8 

2.74 

.83 
1.00 
1.37 
1.70 
2.77 
37.65 
54.20 

Dollars 
.15 
.125 
.14 
.225 
.14 
.945 
1.13 
1.07 

Held  on  100-mesh  
Held  on  150-mesh  
Held  on  200-mesh  
Passed  200-mesh  

True  slime 

Concentrate  on  100-mesh. 

Concentrate  passed  100-mesh  

General  extraction  by  sizing  test                     72.9* 

(%             3.925 

General  extraction  by  assay.  .                      72.8] 

Amalgamation  Tests.*  —  For  making  amalgamation  tests, 
two  methods  may  be  followed.  The  first  is  to  place  6  or  8  assay 
tons  of  the  ore  crushed  to  the  desired  mesh  in  a  large  glass 
bottle  with  sufficient  water  to  make  a  thin  pulp,  adding  |  ounce 
of  mercury.  The  pulp  is  rolled  around  in  the  bottle,  is  lightly 
shaken,  and  is  given  a  panning  motion  for  some  time,  that  all 
the  free  gold  may  be  amalgamated.  The  contents  are  finally 
washed  out  of  the  bottle,  panned  and  repanned  until  the  amalgam 
is  separated  from  the  pulp,  when  the  tailing  is  dried  and  assayed, 
the  difference  between  the  head  and  tailing  assay  representing 
the  amount  amalgamated.  If  mercury  that  contains  no  gold 
has  been  used  in  the  test,  the  gold  in  the  amalgam  can  be  deter- 
mined by  boiling  the  amalgam  in  dilute  nitric  acid  until  only 
the  pure  gold  remains,  when  it  may  be  washed,  dried,  annealed, 
and  weighed  as  usual  in  the  gold  assay;  or  the  amalgam  may 
have  the  mercury  driven  off  by  heating  it  in  the  open  where 
there  is  no  danger  of  salivation,  and  cupeling  the  resulting 
sponge,  which  will  give  both  the  gold  and  silver  amalgamated. 
Mercury  entirely  free  from  gold  can  seldom  be  obtained,  but  can 
easily  be  prepared  by  dissolving  it  in  dilute  nitric  acid,  when  the 
gold  remains  undissolved  and  can  be  filtered  off,  while  the  mercury 

*  From  "  Practical  Stamp  Milling  and  Amalgamation,"  by  the  author. 


78  TEXT  BOOK  OF  CYANIDE  PRACTICE 

can  be  precipitated  by  suspending  a  piece  of  copper  in  the 
solution. 

A  better  method  of  making  an  amalgamation  test  is  to  work 
the  ore  as  a  thin  pulp  in  a  gold  pan  having  an  amalgamated 
bottom,  assaying  before  and  after  treatment;  the  pan  being  used 
to  separate  any  sulphide  present  at  the  same  time.  Laboratory 
amalgamation  tests  as  a  rule  will  not  give  as  high  an  extraction 
as  will  be  obtained  in  actual  mill  practice.  This  may  be  due  to 
the  fact  that  in  preparing  ore  for  such  a  test,  it  is  screened  fre- 
quently, resulting  in  an  evenly-sized  material,  whereas  in  actual 
practice  a  large  proportion  is  crushed  much  finer  and  should  give 
a  higher  extraction.  It  is  also  possible  that  the  dry-crushing 
may  coat  the  gold  with  dirt  or  slime  so  that  to  some  extent  it 
resists  amalgamation. 

Tests  akin  to  amalgamating  in  cyanide  solution  can  be  made 
by  introducing  the  mercury  into  the  bottle  in  which  the  cyanide 
test  is  being  made  and  manipulating  in  the  way  usual  to  both 
tests,  removing  the  amalgam  when  removing  the  cyanide  solu- 
tion. While  this  will  probably  give  the  same  tailing  as  will  be 
obtained  in  actual  practice,  it  will  undoubtedly  give  a  lower 
extraction  by  amalgamation,  due  to  the  slowness  with  which 
the  gold  is  brought  in  contact  with  the  mercury  and  the  long 
continuous  though  slow  action  of  the  cyanide  solution  upon  the 
amalgam. 

Tests  on  Concentrate.  —  In  making  tests  on  concentrate,  it 
should  be  well  washed  and  the  proper  amount  of  lime  added  to 
give  the  solutions  a  protective  alkalinity.  If  the  tests  are  to  be 
by  percolation,  a  .3  (6  pounds),  .6  (12  pounds),  and  a  .9  per  cent 
(18  pounds)  KCN  strength  of  solution  should  be  tried,  while 
lead  acetate  equal  to  1  or  2  pounds  per  ton  of  concentrate  should 
be  added  to  the  solution  to  precipitate  any  alkaline  sulphides 
formed.  The  solution  for  each  test  should  be  kept  separate, 
should  be  run  through  zinc  shavings,  well  aerated,  restandardized, 
and  reused.  The  amount  of  cyanide  used  on  each  test  should 
be  carefully  noted,  and  that  remaining  in  the  solution  after  the 
test  should  be  determined,  thus  enabling  the  cyanide  consump- 
tion to  be  arrived  at.  The  leaching  should  be  continuous  and 
the  charge  drained  at  least  two  or  three  times  daily  to  allow  good 
aeration,  for  this  is  most  necessary  and  should  be  done  mechani- 
cally if  possible.  The  treatment  with  strong  solution  should 


ORE  TESTING  AND  PHYSICAL  DETERMINATIONS    79 

continue  for  twenty  days  and  longer,  until  no  further  extraction 
can  be  secured,  after  which  the  charge  should  be  removed,  dried 
by  air,  and  carefully  sampled,  when  it  may  be  returned  to  the 
percolator  and  a  short  retreatment  tried. 

The  charge  should  be  sampled  daily  by  a  cheese  trier  or  tube 
for  the  first  few  days  of  treatment,  after  which  the  sampling 
periods  may  be  extended  to  every  three  or  four  days.  Agitation 
versus  percolation  should  be  tried,  and  agitation  tests  with 
various  degrees  of  fine-grinding  and  strengths  of  solution  should 
be  experimented  with.  The  agitation  should  be  by  air  or  air 
should  be  supplied  to  the  charge.  Fresh  solution  at  intervals 
is  also  desirable.  The  solutions  should  be  tested  for  alkaline 
sulphides,  reducing  power,  nature  of  cyanicides,  etc.  The  sulphide 
may  be  roasted  and  then  leached  or  agitated,  but  such  roasting 
should  be  a  "  dead  "  or  "  sweet  "  roast,  or  soluble  and  insoluble 
salts,  acting  as  cyanicides,  will  form  and  remain. 

Summary  of  Small  Ore  Tests.  —  The  method  of  testing  an  ore 
may  be  summarized  as  follows:  Test  for  free  acidity  to  learn 
value  of  water-washing.  For  total  acidity  to  learn  probable 
amount  of  neutralizing  agent  required.  Make  bottle  tests  with 
cyanide  solution  and  lime  or  other  neutralizer  in  varying  quanti- 
ties and  starting  with  a  larger  amount  than  that  indicated  by 
the  total  acidity  test.  Make  bottle  or  percolation  tests  with 
•different  strengths  of  solution,  also  determining  the  progress  of 
dissolution.  Make  bottle  or  percolation  tests  on  the  material 
crushed  to  different  degrees  of  fineness,  and  preferably  deter- 
mining the  progress  of  dissolution.  Make  a  test  of  percolation 
against  agitation  on  a  sample  crushed  to  the  fineness  found  to 
give  the  highest  economic  extraction,  to  learn  the  comparative 
extractions  and  rates  of  dissolution.  Make  sizing  tests  before 
and  after  treatment  to  determine  where  the  metal  lies,  and 
possibly  the  presence  of  cyanicides  in  some  particular  size.  Com- 
pare sizing  tests  of  ore  crushed  to  different  degrees  of  fineness. 
Separate  out  the  coarser  sizes  and  treat  separately,  one-half 
without  further  crushing  and  the  other  half  after  being  ground 
finer.  Make  test  to  find  the  maximum  of  extraction  under  ideal 
conditions,  by  samples  ground  to  a  slime,  given  an  oxidizing 
roast,  well  aerated  during  contact  with  solution  and  with  much 
fresh  solution  and  by  adding  2  per  cent  of  potassium  chlorate 
(KC103)  or  sodium  peroxide  (Na2O2)  to  the  charge  as  an  oxidizer, 


80  TEXT  BOOK  OF  CYANIDE  PRACTICE 

using  a  stronger  solution  and  a  continued  contact,  by  heating 
the  solution,  and  by  agitation. 

The  results  of  these  tests  will  check  very  closely  the  extrac- 
tion made  in  actual  plant  practice,  but  the  amount  of  chemicals 
consumed  in  the  laboratory  test  will  be  very  much  higher  than 
those  used  in  actual  practice,  especially  with  reference  to  the 
cyanide. 

Tests  on  Large  Scale.  —  Larger  tests  than  in  bottles  or  per- 
colators should  not  be  made  until  it  has  been  determined  to  what 
degree  of  fineness  the  ore  should  be  crushed,  what  strength  of 
solution  should  be  used,  and  how  fast  the  dissolution  takes  place. 
In  short,  the  larger  tests  should  check  the  results  of  the  more 
easily-made  smaller  tests.  These  larger  tests  are  usually  made 
in  ordinary  wood  tubs  or  those  obtained  by  cutting  barrels  in 
two.  A  filter  bottom  is  placed  in  the  bottom,  also  a  cock  for 
drawing  off  the  solution.  The  tub  is  well  coated  on  the  inside 
with  paraffin  or  waterproof  paint  to  prevent  absorption  of  the 
cyanide  solution.  The  ore  is  charged  into  the  tub  or  vat  and 
the  procedure  conducted  as  with  glass  percolators  and  in  imita- 
tion of  actual  practice.  The  charge  is  sampled  periodically  to 
learn  the  progress  of  dissolution,  while  the  solution  drawn  from 
the  ore  is  tested  for  gold,  silver,  cyanide,  and  protective  alkalin- 
ity. It  is  well  to  make  sizing  tests  in  connection  with  tub  tests. 
Agitation  tests  in  lots  of  ore  of  25  to  100  pounds  should  also 
be  made  if  that  method  of  dissolving  the  gold  and  silver  is  to 
be  used.  Air-lift  agitation  tanks  for  this  purpose  can  easily  be 
constructed.  These  tests  worked  out  by  an  experienced  metal- 
lurgist should  be  sufficient  to  warrant  erecting  a  cyanide  plant 
for  an  easily-worked  gold  ore,  but  it  is  more  advisable  and  with 
base  ores  it  is  necessary  to  make  larger  tests.  These  may  be 
made  in  a  small  experimental  plant  of  500  pounds'  capacity  or 
more,  conducted  as  a  regular  working  plant,  treating  many  charges, 
reusing  the  solution  over  and  over,  and  finally  making  a  clean-up. 
Or  several  tons  of  the  ore  may  be  tested  out  in  a  custom  ore- 
testing  plant  under  the  direction  of  a  well-experienced  metal- 
lurgist. Possibly  it  may  be  well  to  treat  the  ore  in  a  testing 
plant  using  the  same  filtering  and  other  devices  as  it  is  proposed 
to  install. 

Leaching  Rate.  —  The  leaching  rate  is  the  rate  in  inches  per 
hour  that  the  surface  of  a  body  of  solution  standing  over  a  charge 


ORE  TESTING  AND  PHYSICAL  DETERMINATIONS    81 


falls  when  the  charge  is  allowed  to  percolate  as  freely  as  possible. 
The  nearest  that  it  can  be  arrived  at  is  by  preparing  a  pipe,  such 
as  a  water  pipe,  of  as  large  a  diameter  as  is  obtainable  and  with 
a  length  equal  to  that  of  the  proposed  depth  of  charge.  One 
end  of  the  pipe  is  fitted  with  a  leaching  bottom  followed  by  a 
valve.  The  pipe  is  placed  in  an  upright  position  and  filled  with 
ore  to  within  8  inches  of  the  top,  either  dry-filled  or  wet-filled 
with  dilute  pulp,  allowing  the  grains  to  settle  and  arrange  them- 
selves more  compactly  under  water,  as  is  the  method  to  be  used. 
The  charge  is  then  covered  with  water  and  percolation  started, 
the  rate  of  fall  of  the  water  being  noted.  The  leaching  rate 
should  also  be  observed  after  the  charge  has  stood  and  packed 
for  a  few  days. 

In  many  cases  gold  ores  can  be  leached  with  1  ton  of  solution 
to  1  ton  of  ore.  This  means  that  32  cubic  feet  of  water  (1  ton) 
must  pass  through  20  cubic  feet  of  ore  (which  may  be  taken  as 
the  approximate  dimensions  of  1  ton  of  ore  laid  down  in  a  leach- 
ing vat  under  water).  With  a  charge  of  ore  1  foot  deep,  a  column 
of  water  1|  feet  or  19.2  inches  deep  would  have  to  pass  through. 
If  4  days  or  96  hours  are  allowed  for  this,  the  ore  would  have  to 
leach  at  the  rate  of  i  inch  per  hour;  if  the  ore  charge  was  2 
feet  deep  a  column  of  water  38.4  inches  would  have  to  be  passed 
through,  requiring  a  leaching  rate  of  f  inch  per  hour.  From 
this  the  following  table  has  been  worked  out  to  show  the  leaching 
rate  in  inches  required  per  hour  for  passing  1  ton  of  solution 
through  1  ton  of  sand  laid  down  under  water  (20  cubic  feet)  for 
different  depths  of  charge  and  different  lengths  of  time  for  per- 
colation. 


Leaching  Rate  in  Inches  Required  per  Hour  to  Pass  One  Ton  of 

Solution  Through  One  Ton  of  Sand 

Depth  of  Charge  in  Feet. 

Hours  for  Perco- 

lation. 

4 

6 

8 

10 

12 

14 

96 

.8 

1.2 

1.6 

2 

2.4 

2.8 

120 

.64 

.96 

1.28 

1.6 

1.92 

2.24 

144 

.53 

.80 

1.07 

1.33 

1.6 

.87 

168 

.46 

.69 

.91 

1.14 

1.37 

.6 

192 

.4 

.6 

.8 

1. 

1.2 

.4 

216 

.355 

.53 

.71 

.89 

1.06 

.24 

240 

.32 

.48 

.64 

.80 

.96 

.12 

82  TEXT  BOOK  OF  CYANIDE  PRACTICE 

A  study  of  the  above  table  in  connection  with  present  practice 
in  leaching  indicates  the  correctness  of  the  statement  of  Julian 
and  Smart  in  their  work  on  cyaniding,  that  a  leaching  rate  of  3 
inches  per  hour  is  good,  Ij  inches  per  hour  is  fair,  and  J  inch  per 
hour  is  bad  and  usually  uneconomical.  A  leaching  rate  of  IJ 
inches  per  hour  or  better  is  aimed  at  in  well-regulated  plants. 

Slime -settling  Rate.  —  Tests  regarding  the  amount  of  lime  for 
settling  and  time  required  are  made  by  taking  a  sample  of  the 
slime  containing  the  solution  and  dry  pulp  in  the  proportion  to 
be  used,  which  is  usually  four  of  solution  to  one  of  dry  pulp  by 
weight.  The  homogenous  slime  is  divided  to  a  number  of  glass 
jars  or  cylinders,  such  as  1000  c.c.  graduates.  To  the  first  no 
lime  is  added,  to  the  others  lime  is  added  and  well  agitated  in 
the  proportions  of  .1  (2  pounds),  .2  (4  pounds),  .3  (6  pounds),  .5 
(10  pounds),  and  .7  per  cent  (14  pounds)  of  the  dry  pulp,  and 
allowed  to  settle.  At  periods  a  few  hours  apart  the  amount  of 
clear  solution  in  each  sample  is  noted  and  recorded.  At  the 
end  of  the  test  all  clear  solution  is  syphoned  from  the  sample 
which  has  given  the  most  economical  results,  after  which  the 
sample  is  weighed,  dried,  and  reweighed,  to  learn  to  what  per- 
centage of  moisture  the  pulp  has  settled.  The  results  are  usually 
reported  as  the  wet  pulp  equal  to  100  per  cent;  thus  a  pulp  con- 
taining 45  per  cent  moisture  would  contain  55  parts  of  dry 
slime  and  45  parts  of  solution  by  weight. 

Determination  of  the  Cause  of  Low  Extraction.  —  The  cause 
of  low  extraction  or  the  nature  and  condition  of  the  gold  and 
silver  remaining  undissolved  in  the  residue  after  cyanide  treat- 
ment should  be  investigated,  also  the  cause  of  any  abnormal 
consumption  of  cyanide  and  other  chemicals.  The  tests  for 
acidity  will  show  something  of  the  nature  of  the  cyanicides  of  the 
ore,  and  may  indicate  the  need  of  water-washing,  though  such 
procedure  is  not  practiced  except  on  old  pyritic  tailing  or  sul- 
phide that  has  oxidized.  Sizing  tests,  etc.,  may  show  that  the 
ore  requires  fine-grinding  to  liberate  the  value  to  the  solvent 
action  of  cyanide,  that  the  sulphide  should  be  removed  for  more 
prolonged  treatment  with  a  stronger  solution,  or  that  the  re- 
maining value  is  distributed  throughout  all  the  sizes  and  resists 
dissolution,  in  which  case  some  method  of  rendering  the  metal 
soluble  must  be  looked  for.  Stronger  solution  and  longer  con- 
tact may  be  required.  With  very  base  and  arsenical  and  anti- 


ORE  TESTING  AND  PHYSICAL  DETERMINATIONS    83 

monial  ores  it  is  advisable  tQ  test  the  reducing  power  of  the 
solution,  and  for  alkaline  sulphides,  for  the  cause  of  the  low  ex- 
traction may  be  the  abstraction  of  the  oxygen  necessary  for 
dissolution.  In  the  case  of  telluride  ore,  roasting  is  necessary  to 
liberate  the  precious  metal  to  be  dissolved,  or  bromocyanide 
may  be  used.  Some  sulphides,  more  especially  the  arsenical 
and  antimonial  ones,  may  require  roasting.  An  investigation 
into  the  enclosed  or  encased  condition  of  the  precious  metals 
remaining  after  treatment  may  be  made  by  boiling  the  treated 
residue  first  in  diluted  nitric  acid  to  remove  the  silver  and  then 
in  diluted  agua  regia  to  remove  the  gold,  with  assays  before  and 
after  such  treatment. 

Determination  of  the  Cause  of  Cyanide  Consumption.  —  The 
cause  of  cyanide  consumption  may  be  determined  by  taking  100 
grams  of  the  ore  with  100  c.c.  of  new  cyanide  solution  and  agitat- 
ing for  12  to  24  hours,  then  filtering  off  50  c.c.  and  determining 
the  metals  in  it  which  have  combined  with  and  destroyed  the 
cyanogen;  these  will  be  mainly  iron,  copper,  sulphur,  etc.  The 
hydrocyanic  acid  should  also  be  estimated  and  the  solution 
examined  generally. 

Precipitation  Tests.  —  The  solution  from  the  tests  may  be  run 
through  zinc  shavings  in  a  beaker  or  other  receptacle,  care  being 
used  that  all  solution  comes  in  good  contact  for  some  time  with 
the  zinc.  The  zinc  may  then  be  dissolved  in  a  10  to  15  per  cent 
solution  of  sulphuric  acid,  the  resulting  gold  slime  washed,  dried, 
fluxed  as  in  an  assay,  melted,  and  the  button  used  to  check  the 
results.  Tests  on  precipitation  in  the  laboratory  are  practically 
worthless,  for  only  clean  solutions  are  used,  while  in  the  plant 
they  become  charged  with  all  kinds  of  compounds.  Troubles 
with  precipitation  in  actual  practice  can  always  be  worked  out, 
possibly  excepting  some  cases  where  copper  may  interfere;  but 
where  copper  would  interfere  to  this  extent,  its  action  would  be 
so  pronounced  in  the  laboratory  tests  as  to  cause  a  small  plant 
working  a  charge  of  500  pounds  or  more  to  be  installed  for 
thoroughly  testing  out  the  process  preliminary  to  building  the 
regular  plant. 

Tests  During  Plant  Operation.  —  The  methods  spoken  of  do 
not  apply  alone  to  testing  an  ore  preliminary  to  designing  and 
building  a  plant,  but  even  more  so  in  connection  with  the  opera- 
tion of  a  plant.  On  starting  a  plant  the  metallurgist  makes 


84     TEXT  BOOK  OF  CYANIDE  PRACTICE 

many  sizing  and  other  tests  on  the  ore  and  continues  to  make 
them  at  different  times.  The  purpose  of  these  tests  is  to  indicate 
how  to  increase  the  extraction,  lower  the  cost  and  ease  of  oper- 
ating, lessen  the  consumption  of  chemicals,  and  sometimes  to 
increase  the  daily  tonnage  capacity  of  the  plant  without  further 
equipment  and  construction.  While  these  tests  should  be  carried 
on  with  some  regularity  and  without  too  great  a  time  elapsing 
between  new  sets,  they  should  always  be  made  —  and  in  connec- 
tion with  a  watch  over  and  investigation  of  the  solution  —  when 
a  change  in  the  ore  takes  place,  when  a  new  departure  in  plant 
practice  is  being  tried,  when  the  assays  of  the  residue  go  high, 
or  when  erratic  results  are  being  obtained.  Other  things  may 
have  an  indirect  influence,  as  conditions  due  to  a  change  from 
summer  to  winter,  from  the  dry  to  the  rainy  season,  or  even  a 
change  in  mill  employees  who  may  make  some  alterations  that 
pass  by  unnoticed.  At  some  plants  the  head  samples  from  the 
sand-vat  or  agitation  charges  have  been  treated  regularly  over 
long  periods  in  the  laboratory.  The  head  and  tailing  residue 
samples  are  especially  suitable  for  making  sizing  tests  on.  Lab- 
oratory tests  in  connection  with  plant  practice  have  one  end  in 
view  —  what  is  the  highest  extraction  that  can  be  obtained 
under  ideal  conditions  and,  if  the  plant  is  not  making  such  an  ex- 
traction or  duplicating  the  laboratory  results,  what  is  the  reason, 
and  can  the  plant  practice  be  varied  in  a  profitable  way  to  do  so? 
As  these  tests  are  made  with  new  solutions  they  are  a  check 
upon  the  fouling  of  the  mill  solutions.  It  will  be  found  conven- 
ient to  make  up  a  large  quantity  of  solution,  usually  somewhat 
stronger  than  that  used  in  the  plant,  in  a  crock  or  tub  and  use  it 
for  both  dissolving  and  washing  the  value  out  of  the  ore,  making 
the  tests  by  agitation  or  percolation,  preferably  by  agitation 
with  suitable  devices  for  easy  manipulation. 

Specific  Gravity  Determination.  —  A  specific  gravity  determi- 
nation of  slime  is  necessary  to  compute  the  amount  of  dry  slime 
or  pulp  and  of  solution  in  a  charge.  The  specific  gravity  of  any 
substance  is  the  weight  of  that  substance  as  compared  with  an 
equal  volume  of  pure  water  at  its  maximum  density  (4°  C.  or 
39.2°  F.),  which  is  assumed  to  be  the  standard  and  is  given  a 
specific  gravity  of  1. 

To  find  the  specific  gravity  of  dry  pulp  or  ore,  take  a  500-c.c. 
flask,  fill  with  pure  water  to  the  mark,  and  weigh.  Empty  the 


ORE  TESTING  AND  PHYSICAL  DETERMINATIONS    85 

flask,  introduce  a  quantity  of  dry  pulp,  add  sufficient  water  to 
bring  to  the  mark,  and  weigh.     Calculate  the  specific  gravity 
of  the  dry  slime  (which  usually  ranges  between  2.5  and  2.7)  by 
this  formula: 
~  .  ,  Weight  of  dry  pulp  placed  in  flask 

~  Weight  of  flask  when  filled  with  water  + 
Weight  of  dry  pulp  placed  in  flask  - 
Weight  of  flask  filled  with  pulp  and  water. 

As  an  example,  if  flask  filled  with  water  weighs  600  grams,  the 
dry  pulp  used  weighs  100  grams,  and  the  flask  when  containing 
both  pulp  and  water  weighs  660  grams: 


Sp.  gr.  dry  pulp  =  =  2.5. 


'  The  specific  gravity  of  wet  pulp,  such  as  that  in  a  slime  treat- 
ment charge,  is  the  ratio  of  its  weight  to  that  of  the  same  volume 
of  water.  The  measuring  flask  is  filled  to  the  mark  with  a 
sample  of  the  wet  pulp,  great  care  being  used  that  the  sample 
introduced  into  the  flask  is  of  the  same  composition  as  that  in 
the  treatment  charge.  If  the  flask  when  empty  weighs  100 
grams,  it  will  weigh  600  grams  when  filled  to  the  500-c.c.  mark 
with  water.  If  the  flask  filled  with  wet  pulp  weighs  660  grams, 
the  weight  of  the  wet  pulp  is  560  grams,  and  560  :  500  ::  X  :  1, 
or  X  =  1.12,  the  specific  gravity  of  the  wet  pulp,  or: 

Weight  of  wet  pulp 

Sp.  gr.  wet  pulp  =  ^T  .  ,       ,  —   —  :  -  =  —     -*-  —      -  • 
Weight  of  equal  volume  of  water 

The  specific  gravity  of  wet  pulp  may  also  be  obtained  by  means 
of  a  hydrometer,  provided  the  ore  particles  remain  in  suspension 
and  do  not  quickly  settle  out  of  the  solution,  as  would  be  the 
case  with  a  pulp  containing  much  or  coarse  sand. 

The  percentage  by  weight  of  dry  pulp  in  the  wet  charge  is 
obtained  by  this  formula: 
Per  cent  dry  pulp  in  wet  slime 

_  100  (Sp.  gr.  dry  pulp)  (Sp.  gr.  wet  pulp  —  1) 

(Sp.  gr.  wet  pulp)  (Sp.  gr.  dry  pulp  —  1) 
In  the  above  example: 
Per  cent  dry  pulp  in  wet  slime 

100(2.5)  (1.12  -  1)        30 


(1.12)  (2.5  -  1)          1.68 


=  17.9  per  cent. 


86  TEXT  BOOK  OF  CYANIDE  PRACTICE 

This  gives  the  per  cent  of  moisture  in  the  wet  slime  as  100  —  17.9, 
or  82.1. 

The  weight  of  dry  slime  in  a  wet  charge  is  obtained  by  this 
formula : 

Tons  dry  slime  in  charge 

=  Cu.  ft.  in  charge  (Sp'  ffffi Qpulp)  <Sp'  ff'  ^ 

32  (Sp.  gr.  dry  pulp  - 

In  the  above  example: 

Tons  dry  slime  in  charge  of  1  cu.  ft. 

(2.5)  (1.12  -  1)       .3         1 
32(2.5-1)      =  58  =  160 ton 

The  weight  of  solution  in  a  charge  may  be  obtained  by  the 
formula: 

Tons  solution  in  charge 

_  (Cu.  ft.  in  charge)  (Sp.  gr.  dry  pulp  —  Sp.  gr.  wet  pulp) 
32  (Sp.  gr.  dry  pulp  -  1)~~ 

In  the  example: 

Tons  of  solution  in  charge  of  1  cu.  ft. 

=  1  =  1       =  -02875  ton  or  57.5  lb, 


CHAPTER  VIII 
PERCOLATION 

Definition.  —  Cyanide  treatment  by  percolation  consists  in 
placing  the  suitably-prepared  ore  in  a  tank  or  vat  and  allowing 
the  cyanide  solution  to  pass  through  it  by  gravity  in  the  process 
of  dissolving  and  washing  out  the  dissolvable  gold  and  silver. 
The  terms  "  percolation  "  and  "  leaching  "  are  synonymous  in 
cyanidation,  though  percolation  refers  more  to  passing  a  solution 
through  a  porous  substance,  as  sand,  and  leaching  to  the  dis- 
solving and  removing  of  some  substance  or  substances  from  the 
material  through  which  the  solution  is  passing  or  percolating. 
The  container  holding  the  ore  for  treatment  by  percolation  may 
be  called  a  "  vat  "  rather  than  a  "  tank,"  the  word  "  tank  " 
referring  to  agitation  tanks  for  the  treatment  of  slime  and  more 
especially  to  tanks  holding  solution. 

Percolation  of  ore  divides  into  two  classes:  the  treatment  of 
ore  delivered  dry  into  a  vat,  and  the  treatment  of  ore  delivered 
wet  and  flowing  into  a  vat.  Under  the  first  head  comes  ore 
from  tailing  ponds  and  deposits,  and  from  dry-crushing  mills; 
under  the  second  head  come  ore  and  tailing  delivered  wet  as  a 
flowing  pulp  from  the  mill  to  the  vats.  The  system  of  collecting 
in  one  vat  and  transferring  the  drained  but  still  wet  sand  to 
another  vat  for  percolation  —  the  double-treatment  system  - — 
may  be  said  to  be  a  combination  of  the  two. 

Treatment  of  Tailing  Deposits.  —  Practically  all  of  the  old 
tailing  deposits  have  been  treated,  but  work  of  this  nature  will 
always  be  carried  on  to  some  extent,  as  new  mills  making  a  good 
extraction  by  amalgamation  and  concentration  are  not  always 
ifr  a  position  to  put  in  a  cyanide  annex  at  once.  At  other  places 

e  value  of  the  mill  tailing  may  be  considered  too  low  to  treat 
b;  r  cyanide  unless  the  output  be  large,  which  may  require  years 
o  development  and  small  capacity  to  indicate.  Mill  tailing 

at  has  not  been  cyanided  and  that  contains  80  cents  or  more  in 
precious  metal  may  be  considered  as  offering  opportunities  for 

87 


88  TEXT  BOOK  OF  CYANIDE  PRACTICE 

profitable  cyanidation,  if  in  sufficient  quantity,  and  should  there- 
fore be  stored  if  not  treated  at  once.  Even  the  discharged  tailing 
residue  from  cyanide  plants,  when  still  carrying  material  value, 
may  be  stored  with  the  hope  that  the  passing  of  time  will  render 
the  remaining  precious  metal  soluble  through  oxidation  or  other- 
wise, or  that  some  new  process  may  be  devised  whereby  the  value 
may  be  obtained. 

The  principal  problem  in  the  treatment  of  tailing  deposits  is  to 
get  an  easily-leached  charge  in  the  vats.  Most  tailings  are  care- 
lessly banked,  resulting  in  a  segregation  of  the  sand  and  slime  in 
separate  parts  of  the  pond,  the  slime  forming  a  leathery  imper- 
meable mass  impossible  to  leach  unless  by  manipulation  in  connec- 
tion with  the  sand.  The  segregation  of  sand  and  slime  is  owing  to 
the  tailing  flow  being  introduced  at  one  point  in  the  pond  and  the 
overflowing  water  being  deducted  at  another  point.  The  heavy 
sand  naturally  settles  at  the  point  of  introduction,  the  sand 
diminishing  in  quantity  and  coarseness  and  the  amount  of  slime 
increasing  as  the  point  of  overflow  is  reached,  about  which  is 
usually  pure  slime.  The  segregation  in  this  manner  can  be  pre- 
vented by  having  a  number  of  inflow  and  outflow  points  spaced 
evenly  about  the  pond,  changing  the  flow  points  daily  or  oftener. 
This  will  result  in  throwing  a  layer  of  sand  on  a  stratum  of  slime 
into  which  it  will,  to  some  extent,  sink  with  some  evenness  over 
all  the  pond. 

Slime  which  has  settled  in  large  deposits  cannot  be  leached  in 
connection  with  sand  unless  it  is  finely  disintegrated.'  This  has 
sometimes  been  accomplished  by  plowing  and  harrowing  the 
slime  and  then  mixing  it  with  the  sand.  But  this  procedure  is 
not  always  a  success  owing  to  the  cost,  the  poor  disintegration, 
and  the  inability  to  get  a  good  admixture.  Where  the  sand  and 
slime  have  been  settled  in  the  pond  with  as  thorough  an  ad- 
mixture as  possible,  if  the  mere  process  of  shoveling  or  scraping 
up  the  material  to  effect  its  removal  to  the  leaching  vat  is  not 
sufficient  to  disintegrate  the. slime  and  mix  it  with  the  sand  for 
a  good  leaching  product,  plowing  and  harrowing  in  connection 
with  sun-drying  should  do  so. 

The  amount  of  slime  that  can  be  successfully  leached  with  sand 
in  a  dry-filling  percolation  plant  is  large  but  variable.  Slime, 
as  referring  to  that  part  of  mill  pulp  which  muddies  water  and 
does  not  readily  settle  and  not  to  any  particular  degree  of  fine- 


PERCOLATION  89 

ness,  is  of  a  variable  nature,  but  seems  to  be  divided  into  two 
classes:  a  siliceous  slime,  a  slime  produced  by  the  fine  crushing 
of  a  hard  siliceous  rock,  and  a  clay  slime,  resulting  from  a  talcose, 
clayey  ore.  A  siliceous  slime  is  of  a  more  granular,  leachable, 
and  quickly-settled  nature.  Ore  making  such  a  slime,  when  it  is 
crushed  through  a  30  or  40-mesh  screen  and  properly  settled  in  a 
tailing  pond,  should  leach  well  in  a  percolation  vat.  But  the 
handling  of  a  clay  slime  which  is  of  a  more  flocculent  and  slowly- 
settling  nature,  and  usually  occurs  in  large  quantities,  is  a  more 
difficult  problem. 

Percolation  vats  are  filled  from  tailing  deposits  by  shoveling 
and  earring,  or  more  usually  by  wheel  scrapers.  The  material, 
with  reference  to  its  coarseness  or  fineness,  must  be  distributed 
evenly  over  the  area  of  the  vat,  or  the  percolating  solution,  follow- 
ing the  lines  of  least  resistance,  will  leach  through  the  coarse 
material,  shunting  the  fine  or  slime  material  and  producing  un- 
satisfactory results.  If  the  material  must  be  varied  in  the  same 
vat,  it  should  be  by  a  layer  of  even  thickness  over  the  whole  area 
of  the  vat.  No  lumps  or  clots  of  slime  should  go  into  the  vat, 
for  they  will  absorb  the  solution  and,  from  their  unleachable 
character,  will  not  allow  it  to  be  displaced;  thereby  causing  a 
loss  of  cyanide  and  leaching  capacity  and  giving  practically  no 
extraction. 

Treatment  of  Dry-crushed  Ore.  —  Ore  that  has  been  dry- 
crushed  is  delivered  to  the  vats  by  cars  or  belt-conveyors,  and  is 
invariably  homogenous,  so  that  a  uniform  leaching  rate  all  over 
the  vat  is  to  be  had.  Also,  the  sand  and  slime  portions  of  the 
ore  are  so  well  mixed  that  together  they  form  an  easily-perco- 
lated material,  allowing  the  cyanide  solution  to  penetrate  the 
ore  and  dissolve  the  metals,  and  then  to  be  displaced  and  well 
washed  out  together  with  the  dissolved  metals.  Ore  treated  by 
dry-crushing  and  percolation  is  seldom  crushed  finer  than  40- 
mesh  and  is  being  less  and  less  resorted  to,  for  the  ease,  economy, 
and  satisfaction  of  fine  wet-crushing  in  comparison  with  fine 
dry-crushing,  and  the  ability  of  the  filtering  devices  to  handle 
finely-crushed  material,  giving  a  high  dissolution  of  the  precious 
metals,  is  making  dry-crushing  uneconomical.  The  slimy  ma- 
terial made  in  dry-crushing  seldom  gives  any  trouble  in  leaching, 
except  in  some  cases  where  the  clay  slime,  though  evenly  and 
thoroughly  mixed  with  the  sand,  tends  to  absorb  the  solution 


90 


TEXT  BOOK  OF  CYANIDE  PRACTICE 


and  agglomerate,  so  that  a  thorough  washing  cannot  be  made. 
Such  ores  do  not  often  occur,  but  when  found  should  be  filtered 
by  the  vacuum  or  pressure  leaf-filter,  for  they  settle  too  slowly 
and  retain  too  much  moisture  to  be  treated  by  decantation,  and 
cannot  be  washed  to  an  advantage  in  the  ordinary  way  in  a  plate 
and  frame  filter-press. 

Direct-Filling  of  Vats  with  Wet  Pulp.  — In  the  wet-filling  of 
vats,  the  pulp  flowing  from  the  wet-crushing  mill  is  delivered  to 
the  vat  by  a  revolving  distributor;  in  some  cases  by  a  movable 
hose  placed  in  different  parts  of  the  vat,  a  plan  not  to  be  recom- 
mended. This  distributor,  known  as  the  Butters  and  Mein  or 


Fig.  1.— The  Butters  and  Mein  Automatic  Sand  Distributor  (Pacific  Tank 

and  Pipe  Co.). 

garden-sprinkler  type,  Fig.  1,  consists  of  a  revolving  basket  or 
hopper  placed  over  the  exact  center  of  the  vat.  Pipes  of  uneven 
lengths  ending  in  pipe  elbows  radiate  from  the  basket.  The  mill 
pulp  is  led  into  the  basket  or  hopper  by  a  launder  and  runs  out 
through  the  pipes  and  elbows  into  the  vat.  The  hydrostatic  head 
of  the  pulp  in  the  basket,  in  connection  with  the  right  angles  of 
the  elbows  from  which  the  pulp  flows,  causes  the  distributor  to 
revolve  as  a  garden  sprinkler  does,  delivering  the  pulp  to  the  vat 
in  a  series  of  various-sized  rings  about  the  center.  As  first  used, 
the  pulp  without  classification  was  run  through  the  distributor 
into  the  vat,  the  surplus  water  and  part  of  the  slime  overflowing 


PERCOLATION  91 

the  rim  or  edge  of  the  vat  into  an  annular  launder;  the  overflow 
edge  of  the  vat  consisting  of  a  tongue  or  strip  of  wood  that  could 
be  moved  up  or  down  or  planed  off  that  the  slime  water  might 
overflow  evenly  at  all  points  about  the  circumference  of  the  vat. 
This  method  resulted  in  the  deposition  of  a  large  quantity  of 
slime  with  the  sand.  The  slime  deposition  was  uneven  from  the 
center  to  the  circumference  of  the  vat,  owing  to  the  flow  of  water 
from  the  center  towards  the  rim.  These  tended  to  cause  uneven 
filling  and  poor  leaching.  As  at  present  used,  the  mill  pulp  is 
passed  through  classifying  cones,  spitzkastens,  or  mechanical 
classifiers,  which  remove  as  much  of  the  slime  as  possible.  The 
sand  flows  through  the  distributor  into  the  vat,  from  wrhich  the 
overflow  carrying  some  slime  and  fine  sand  is  over  the  rim  into 
an  annular  launder  or  through  small  decantation  pipes  at  the 
rim  of  the  vat,  or  through  a  standpipe  in  the  center  of  the  vat  and 
underneath  the  distributor.  There  has  been  used  in  vats  collect- 
ing the  sand  for  removal  to  the  regular  treatment  vats  a  slat  gate 
or  window  in  the  side  of  the  vat  extending  from  the  top  to  the 
bottom,  which  is  closed  by  a  canvas  curtain  gradually  unrolled 
and  held  in  place  by  the  sand  as  it  rises  in  the  vat. 

It  can  be  understood  that  there  are  objections  to  all  of  the 
above  methods.  To  obtain  good  and  satisfactory  percolation, 
two  things  are  necessary:  first,  a  sand  that  is  absolutely  free 
from  unleachable  slime,  a  sand  that  is  clean  and  sharp  no  matter 
how  fine  it  may  be;  and  second,  an  even  distribution  of  that 
sand  in  the  vat.  Cone  classifiers  have  in  some  cases  made  a  very 
clean  separation  of  sand  and  slime,  but  generally  are  not  highly 
efficient.  However,  the  Dorr  classifier,  as  shown  in  Fig.  2,  of  the 
drag  type  of  classifiers,  gives  an  almost  absolutely  clean  sand  and 
a  true  slime,  thereby  fulfilling  the  first  requirement.  The  usual 
methods  of  running  sand  distributors  do  not  give  the  best  distri- 
bution of  sand  in  the  vat.  A  large  volume  of  water  or  very  dilute 
pulp  is  used  to  operate  the  distributor;  this  creates  a  current  from 
the  center  of  the  tank  to  the  rim  overflow,  causing  the  fine  sand 
to  travel  away  from  the  point  where  it  strikes  the  surface  of  the 
water  filling  the  vat  toward  the  overflow,  and  some  even  being 
carried  out  of  the  vat.  Variations  in  the  charge  are  also  caused 
by  the  stoppage  of  the  distributor  at  times.  By  arranging  the 
distributor  to  be  driven  by  power  and  running  the  sand  delivered 
by  the  Dorr  classifier  down  a  steep  grade,  with  as  little  water  as 


92 


TEXT  BOOK  OF  CYANIDE  PRACTICE 


possible,  into  the  distributor  and  vat,  an  almost  perfect  leaching 
charge  can  be  obtained.  The  Dorr  classifier  makes  a  clean  sepa- 
ration of  sand,  while  the  small  amount  of  water  used  to  convey 
the  sand  through  the  distributor  into  the  vat  does  not  create  a 
current,  thus  allowing  even  the  fine  sand  to  settle  where  it  strikes 
the  water  in  the  vat,  while  the  small  overflow  is  almost  clear 
water.  This  method  of  deposition  allows  the  filling  of  a  vat  to 


Fig.  2.  — The  Dorr  Classifier. 

be  begun  without  first  filling  with  water,  to  assist  in  the  classi- 
fication as  must  be  done  when  using  cone  classifiers,  and  does 
not  introduce  difficulties  by  depositing  a  layer  of  slime  when  the 
mill  is  temporarily  shut  down. 

The  present  practice  is  to  prevent  as  much  as  possible  any 
slime  from  getting  into  the  sand  charge,  but  in  some  plants  the 
sand  is  rather  crudely  settled  in  collecting  vats  and  transferred 
thence  to  final-treatment  vats  by  hand  or  mechanical  digging 
and  conveying  appliances.  This  transfer  effects  a  thorough 
mixing  of  the  coarse  and  fine  sand  and  the  slime;  it  also  makes 
the  charge  more  readily  leached  by  increasing  the  voids  or  in- 
terstices between  the  grains  of  pulp.  When  sand  is  settled  under 
water,  the  grains  arrange  themselves  very  compactly,  thereby 
hindering  percolation  and  aeration,  but  when  a  drained  charge 
has  been  transferred  to  another  vat  it  will  occupy  probably  from 
10  to  20  per  cent  more  space  (after  it  has  subsided  on  the  intro- 
duction of  the  first  solution).  Similarly,  the  ores  from  tailing 


PERCOLATION  93 

deposits  or  dry-crushing  mills  when  dry-filled  into  the  vats  will 
probably  occupy  from  10  to  20  per  cent  more  space  than  when 
wet-filled  —  the  increase  is  variable.  The  transfer  from  the 
collecting  to  the  final-treatment  vat  also  aerates  the  charge, 
though  this  can  be  well  effected  in  other  ways.  By  the  use  of  a 
good  method  of  wet-filling,  all  necessity  of  transferring  the  charge 
may  be  done  away  with. 

Depth  of  Sand  Charge.  —  It  is  hard  to  say  what  is  the  maxi- 
mum depth  of  charge  that  can  be  leached.  As  the  depth  of  the 
charge  becomes  greater,  the  pressure  in  the  lower  part  of  the 
charge  from  the  ore  above  becomes  heavier,  causing  the  voids  or 
interstices  in  the  ore-charge  to  become  smaller  and  thereby 
hindering  percolation.  This  must  especially  be  taken  into 
account  in  treating  ores  containing  slime,  as  from  tailing  deposits 
or  dry-crushing  mills,  also  finely-ground  sand,  for  as  the  ore  is 
ground  finer  or  the  amount  of  slime  is  increased,  the  voids  or 
interstices  become  smaller.  The  higher  the  percentage  of 
moisture  retained  by  the  drained  charge,  the  lower  will  be  the 
leaching  rate  and  the  less  easily  will  the  charge  be  leached.  It  is 
likewise  hard  to  say  what  is  the  maximum  fineness  of  ore  that 
can  be  leached.  No  unsatisfactory  results  have  been  reported 
from  leaching  fine  sand;  it  has  been  found  that  clean,  sharp  sand 
ground  to  200-mesh  can  be  leached.  The  question  of  leaching 
ore  depends  not  so  much  on  the  fineness  of  the  material,  as  on 
the  amount  of  flocculent  slime,  the  total  absence  of  which  gives 
ideal  conditions  for  leaching.  The  leaching  rate  has  been  de- 
fined and  the  bearing  on  it  of  the  volume  of  solution  to  be  passed 
through  the  charge,  which  has  a  most  important  influence  on  the 
depth  of  charge  permissible,  has  been  discussed  under  Ore  Test- 
ing and  Physical  Determinations.  Six  feet  was  the  standard 
depth  of  leaching  vats  for  a  long  time,  but  sand  crushed  very  fine 
is  now  being  leached  in  charges  10  feet  deep,  and  vats  14  feet  in 
depth  are  in  use. 

Arrangement  of  Leaching  Plant.  —  Fig.  3  represents  the  usual 
plan  of  a  leaching  plant,  while  Fig.  4  shows  its  elevation.  Figs.  5 
and  6  show  elevations  of  plant  arrangement  that  are  permissible, 
but  not  as  convenient  as  in  Figs.  3  and  4.  However,  the  ar- 
rangement in  Figs.  5  and  6  is  often  used  where  it  is  required  by 
the  surface  configuration  or  the  arrangement  of  the  mill.  The 
solution  tanks  supplying  the  leaching  vats  are  always  called 


94  TEXT  BOOK  OF  CYANIDE  PRACTICE 

"  stock  tanks  "  or  "  storage  tanks,"  preferably  the  former.     The 
tanks  receiving  the  enriched  solution  as  it  drains  from  the  ore 


Leaching  Vat 


I  Sump  Tank  I 


Figs.  3  and  4.  —  Arrangement  of  Leaching  Plant. 

and  which  act  as  reservoirs  forx  the  zinc  boxes  are  called  "  gold 
tanks."  The  tanks  following  the  zinc  boxes  are  called  "  sumps  " 
or  "sump  tanks,"  when  in  the  lowest  part  of  the  plant. 

Weak  and  Strong  Solution  and  Their  Separation.  —  It  was 
formerly  the  custom  in  all  plants  to  separate  the  solution  into 


PERCOLATION 


95 


two  parts,  a  "  weak  "  and  a  "  strong  "  solution,  separate  tanks 
and  pipe  systems  being  provided  for  each.  The  proportion  of  these 
solutions  was  equal  or  unequal,  —  usually  equal,  —  as  appeared 
best  or  convenient  in  the  plant  practice.  Whatever  proportions 
were  used  were  kept  constant  by  turning  the  solutions  flowing 
from  the  treatment  vats  into  the  "  strong  gold  tank  "  when 
they  were  high  in  cyanide  strength,  and  into  the  "  weak  gold 
tank  "  when  low  in  cyanide,  keeping  one  as  high  in  cyanide  and 


Leaching  Vat 


Leaching  Vat 


I  Stock  Tank  I 


Figs.  5  and  6. — Arrangement  of  Leaching  Plant. 

the  other  as  low  as  possible.  The  "  weak  solution  "  was  in 
many  cases  used  with  a  high  protective  alkalinity  as  the  first 
solution  on  the  ore,  being  a  sort  of  an  alkaline  wash  to  neutralize 
the  acidity  of  the  ore,  with  a  less  consumption  of  cyanide,  than 
if  strong  solution  was  introduced  before  the  cyanicides  had  been 
largely  neutralized.  And  in  all  cases  the  weak  solution  was  used 
jas  the  final  solution  washes,  thereby  lowering  the  amount  of 
cyanide  to  be  displaced  by  the  final  water  washes,  and  effecting 
a  considerable  saving  in  the  amount  of  cyanide  mechanically 
lost,  through  being  discharged  as  the  moisture  in  the  tailing  resi- 
due. It  can  be  understood  that  there  must  be  some  action  by 
the  cyanide  upon  the  metals  and  other  substances  in  the  ore  every 
time  the  solution  is  brought  in  contact  with  the  ore,  and  that 
this  action  is  proportional  to  the  strength  of  the  solution:  con- 


96  TEXT  BOOK  OF  CYANIDE  PRACTICE 

sequently  the  use  of  a  weak  solution  instead  of  a  strong  one,  for 
washing  out  the  value  after  it  is  dissolved,  must  effect  a  saving 
in  the  cyanide  chemically  used  and  lost.  The  additional  solid 
cyanide  is  always  added  to  the  strong  or  dissolving  solution. 
When  it  was  customary  to  use  solutions  of  .2  per  cent  (4  pounds), 
and  .25  per  cent  (5  pounds)  for  the  dissolving,  a  material  saving 
in  the  cost  of  cyanide  was  made  by  the  division  into  two  strengths 
of  solution,  but  since  it  has  become  common  to  use  solutions 
having  a  maximum  strength  of  .1  per  cent  (2  pounds)  on  gold 
ores,  the  division  has  in  many  cases  been  abandoned.  Especially 
where  the  problem  of  differentiating  into  a  weak  and  strong 
solution  has  been  complicated  by  the  slime-treatment  system  or 
the  necessity  of  having  all  the  solution  carry  a  substantial  cyanide 
strength  to  get  a  good  precipitation.  Still  it  may  be  said  that 
the  division  is  practiced  wherever  it  is  possible  and  economical 
to  do  so. 

Application  of  Solution  to  Treatment  Vats.  —  The  first  solu- 
tion run  to  treatment  vats  filled  with  dry  ore  is  invariably  from 
the  bottom,  being  introduced  underneath  the  filter  bottom  to 
gradually  rise  up  through  the  ore  and  appear  on  the  surface  of 
the  charge.  There  are  several  good  reasons  for  this.  The  solu- 
tion is  usually  started  running  long  before  the  vat  is  filled  and 
leveled  off,  the  bottom  of  the  charge  thereby  gets  a  much  longer 
time  of  treatment  than  the  upper  part,  a  desirable  thing,  as  the 
bottom  of  the  charge  is  packed  tighter  by  the  weight  above  it 
and  is  seldom  well  drained,  in  consequence  receiving  less  aera- 
tion and  having  a  slower  dissolving  rate.  The  charge  subsides 
to  a  very  large  extent  —  as  much  as  10  per  cent  —  as  the  solu- 
tion rises,  thereby  allowing  the  tanks  to  be  filled  with  more  ore 
than  if  the  first  charge  of  solution  was  run  on  from  the  surface. 
This  subsidence  is  a  gradual,  easy  movement  of  the  particles  of 
ore  adjusting  themselves,  whereas,  was  the  solution  run  on  from 
the  top,  there  would  be  a  fissuring,  channeling,  and  uneven 
packing  of  the  charge.  To  the  casual  observer  these  would  be 
of  no  moment,  but  they  do  cause  irregular  percolation  and  extra 
labor.  It  has  been  said  that  advantage  should  be  taken  of  the 
air  in  the  voids  or  interstices  of  the  ore  by  running  the  solution 
on  top  of  the  charge,  letting  the  air  bubble  up  through.  The 
theory  of  aeration  in  cyanide  practice  is  sufficiently  settled  to 
say  that  if  the  solution  had  been  allowed  the  usual  opportunity 


PERCOLATION  97 

to  aerate,  it  would  now  absorb  no  more  oxygen,  and  that  the  free 
air  bubbling  up  could  not  assist  in  dissolving  gold  that  was  not 
yet  in  a  condition  akin  to  a  nascent  state  and  ready  to  go  into 
solution  through  having  been  acted  upon  by  the  cyanide.  The 
solution  must,  of  course,  be  allowed  to  rise  until  it  covers  the  whole 
surface  of  the  ore  charge,  and  with  dry-filled  ore  until  it  is  ready 
to  overflow  the  vat,  for  the  first  solution  passing  through  the 
charge  and  appearing  on  the  surface  must  necessarily  have  much 
of  its  cyanide  strength  destroyed.  The  ore  charge  is  carefully 
leveled  off  during  the  filling  process  if  dry-filled,  or  after  the 
water  has  disappeared  from  the  surface  of  the  charge  for  some 
time  in  the  process  of  draining  if  wet-filled.  The  leveling  being 
done  by  shoveling,  hoeing,  or  raking  the  charge.  High  spots 
in  a  vat  of  dry-filled  ore  may  be  leveled  at  the  time  the  solution 
appears  on  the  surface,  or  at  the  culmination  of  the  wet-filling 
of  a  vat,  by  pressing  and  working  the  high  spots  of  ore  with  the 
flat  surface  of  a  hoe  pressed  vertically  downwards,  without 
harming  the  charge  for  good  leaching  purposes.  The  more 
perfect  the  method  of  filling,  including  adjusting  the  discharge 
from  the  pipes  of  the  automatic  distributor,  the  less  leveling 
will  be  required. 

Where  the  ore  is  wet-filled  into  the  treatment  vats,  the  first 
solution  is  run  on  from  the  top,  for  the  reason  that  it  is  more 
convenient  to  displace  the  moisture  in  the  ore  in  this  way  and 
draw  it  off  from  the  bottom  of  the  vat.  The  ore  charge  being 
perfectly  settled  and  the  grains  of  ore  arranged  closely  and 
firmly  together  in  the  process  of  filling  and  settling  under  water, 
there  is  no  subsiding,  settling,  channeling]  or  fissuring  of  the 
charge  as  would  occur  with  dry-filled  ore.  Ore  transferred  wet 
into  treatment  vats  from  collecting  vats  usually  receives  its  first 
solution  on  top  of  the  charge,  though  it  can  be  more  advanta- 
geously introduced  from  the  bottom  if  means  are  provided  for  draw- 
ing off  the  displaced  moisture  and  weakened  and  diluted  solution 
that  appears  above  the  charge. 

Ore  that  has  been  filled  into  the  vats  dry  must  contain  its 
soluble  or  free  acidity  that  is  removable  by  water-washing,  and 
its  insoluble  latent  acidity,  the  two  forming  the  total  acidity 
which  an  alkali  would  neutralize.  The  total  acidity  represents 
a  large  part  of  the  cyanicides  of  the  ore,  to  which  may  be  added 
the  other  cyanicides  which  destroy  cyanide  and  cannot  be  re- 


98  TEXT  BOOK  OF  CYANIDE  PRACTICE 

moved  or  neutralized  by  an  alkali,  such  as  copper  and  some  of 
the  base-metal  compounds.  When  the  ore  is  crushed  in  water 
and  immediately  conveyed  to  the  leaching  vats,  nearly  all  the 
soluble  or  free  acidity  is  washed  out;  but  not  the  latent  or  in- 
soluble acidity  or  the  nonacid  cyanicides,  though  the  first  is 
neutralized  to  quite  an  extent  by  any  lime  or  alkali  added. 
Where  the  crushed  ore  is  allowed  to  stand  in  tailing  ponds,  new 
free  or  soluble  acidity  is  developed.  Where  the.  ore  is  crushed 
in  cyanide  solution  and  delivered  to  sand  vats,  the  free  and 
latent  acidity  is  largely  neutralized  and  washed  out  by  cyanide 
and  lime  or  alkalinity  in  the  solution. 

A  consideration  of  the  above  principles  in  connection  with 
those  given  under  Alkalinity  and  Lime  gives  a  clue  to  the  proper 
use  of  lime  or  other  neutralize^  and  as  to  the  nature  of  the  first 
solution  to  be  used  on  the  ore,  whether  high  or  low  in  cyanide  or 
in  protective  alkalinity.  If  the  dry-crushed  ore  contains  an 
extraordinarily  large  amount  of  free  acidity,  it  should  first  be 
water-washed  to  remove  it.  If  the  water  wash  or  final  water 
wash  be  alkaline,  or  lime  slacked  as  a  fine  powder  and  well 
mixed  has  been  added  to  the  ore,  the  latent  acidity  will  also  be 
neutralized  leaving  only  the  nonacid  cyanicides  and  new  acidity 
which  may  be  generated.  Water  washes  to  remove  the  acidity 
are  now  seldom  used,  except  in  treating  concentrate  or  old 
pyritic  tailing.  Their  use  on  dry-filled  ore  increases  the  amount 
of  plant  solution  so  that  little  or  no  water  may  be  used  for  the 
final  wash  before  discharging  the  tailing  or  residue,  thereby 
causing  a  higher  mechanical  loss  of  cyanide.  Consequently, 
under  the  above  conditions,  a  solution  low  in  cyanide  and  strongly 
alkaline  is  run  on  the  ore.  As  soon  as  the  solution  appears  at 
the  surface  of  the  charge,  if  it  has  been  absolutely  necessary  to 
introduce  it  from  the  bottom,  the  introduction  is  changed  from 
the  bottom  to  the  top  of  the  charge,  the  drain  valve  is  opened, 
and  the  weak  solution  is  allowed  to  percolate  through  the  charge, 
destroying  the  total  acidity  in  the  charge  by  its  alkalinity  and 
that  of  the  lime  added  to  the  charge.  The  acid-destroying 
solution  wash  is  allowed  to  run  through  the  charge  until  the 
drainings  show  a  slight  protective  alkalinity,  when  the  solution 
is  allowed  to  sink  below  the  surface  of  the  charge  for  some  time, 
before  being  followed  by  the  strong  solution  upon  which  the 
main  dissolution  of  the  gold  and  silver  is  relied.  It  can  be 


PERCOLATION  99 

understood  that  this  method  of  using  a  first  wash  of  weak  solu- 
tion is  for  the  purpose  of  reducing  the  consumption  of  cyanide, 
and,  as  it  involves  some  time  and  labor  and  may  be  otherwise 
undesirable,  it  is  not  often  followed.  In  some  cases  with  wet- 
filled  ore  this  first  wash  or  alkaline  solution  is  treated  as  a  sepa- 
rate and  third  nature  of  solution,  to  precede  the  strong  solution 
as  an  alkaline  wash  and  to  follow  the  weak  solution  as  a  final 
water- wash,  being  precipitated  only  before  use  as  a  final  wash. 
Laboratory  investigations  regarding  the  free  and  latent  acidity 
and  the  nonacid  cyanicides  and  the  consumption  of  chemicals  by 
each  will  indicate  the  procedure  that  may  be  advisable,  but  the 
results  in  actual  practice  by  comparative  tests  and  tests  upon 
the  solutions  should  determine  the  plant  procedure.  With 
silver  ores  it  is  generally  advisable  to  start  off  with  a  strong 
solution  that  will  dissolve  and  hold  the  silver  in  solution,  and 
not  so  weak  as  to  allow  it  to  be  reprecipitated,  by  the  alkaline 
sulphides,  about  the  remaining  silver  as  a  film  of  silver  sulphide 
rather  hard  to  redissolve. 

Ore  crushed  in  water  and  wet-filled  into  leaching  vats  may  be 
taken  as  the  type  case  of  how  leaching  practice  or  treatment  is 
conducted.  Immediately  upon  the  filling  of  one  vat  the  pulp 
flow  is  turned  to  another.  The  drain  cock  of  the  filled  vat  is 
opened  while  all  the  water  possible  is  syphoned  from  the  top  of 
the  sand  charge  by  a  hose  or  decanting,  pipes  in  the  rim  of  the 
vat.  As  soon  as  the  surface  of  the  charge  is  sufficiently  dry,  it 
is  leveled.  When  the  charge  is  well  drained  of  its  moisture  as 
indicated  by  the  discharge  from  the  drain  valve,  usually  requiring 
from  eight  to  eighteen  hours,  the  first  solution  is  run  on  top  of  the 
charge  from  the  strong-stock  or  storage  tank,  presuming  the 
strong  solution  is  used  first.  This  first  solution  is  "  standard- 
ized "  or  brought  up  to  the  standard  of  the  maximum  strength 
considered  necessary  to  dissolve  the  precious  metals.  .  To  do 
this  the  "  solution  man  "  in  charge  of  the  work  for  the  shift 
undar  the  plant  superintendent,  roughly  mixes  the  contents  of 
the  strong-stock  tank  and  drops  a  bottle  attached  to  a  string  or 
pole  into  various  parts  of  the  tank  to  obtain  an  average  sample 
of  the  solution.  The  solution  is  tested  for  its  strength  in  free 
cyanide,  and  possibly  for  its  total  cyanide  if  that  is  being  taken 
into  account  by  the  metallurgist  in  charge.  The  tonnage  of 
solution  is  noted  from  a  telltale  and  scale  upon  the  side  of  the 


100  TEXT  BOOK  OF  CYANIDE  PRACTICE 

tank,  or  by  plunging  into  the  solution  a  measuring  stick  gradu- 
ated to  show  the  amount  of  solution  in  tons.  The  requisite 
amount  of  cyanide  is  now  added  to  bring  the  solution  up  to  the 
desired  strength.  It  may  be  added  by  dissolving  the  solid  salt 
in  a  small  "  dissolving  tank  "  set  above  and  emptying  into  the 
strong-stock  tank,  with  tables  and  scales  prepared  that  give  the 
amount  of  concentrated  solution  required  to  bring  the  strong 
solution  up  to  the  standard.  The  cyanide  may  also  be  added  to 
a  perforated  box  or  metal  basket  hanging  in  the  flow  into  the 
strong-stock  tank,  or  it  may  be  placed  in  such  a  receptacle  sus- 
pended in  the  solution  and  occasionally  juggled  up  and  down  by 
the  solution  man.  After  the  cyanide  has  been  added  and  dis- 
solved, the  strong-stock  solution  is  agitated  to  render  the  solution 
homogeneous  in  strength  by  a  board  attached  to  a  pole  as  a  hoe 
or  by  a  very  short  air  agitation. 

In  running  solution  on  leaching  vats,  the  whole  surface  of  the 
charge  should  be  covered  as  quickly  as  possible,  for  if  more  solu- 
tion disappears  at  one  part  of  the  surface  than  another,  that  part 
is  better  treated  by  being  washed  freer  of  dissolved  metals  than 
the  other  part.  Where  a  percolating  charge  is  supplied  by  small 
solution  pipes,  this  may  cause  serious  trouble,  but  can  to  some 
extent  be  remedied  pending  the  installation  of  larger  pipes  by 
closing  the  drain  cock,  saturating  the  charge,  and  flooding  it  with 
solution  until  the  vat  will  hold  no  more,  and  allowing  the  solution 
upon  draining  to  run  into  the  vat  until  ready  to  disappear  below 
the  surface  of  the  charge.  The  vat  may  be  drained  each  time 
and  then  closed  for  a  repetition  of  the  above,  or  when  the  solu- 
tion is  ready  to  disappear  from  the  surface  of  the  charge  the 
drain  cock  may  be  closed  until  the  depth  of  the  solution  above 
the  charge  can  be  raised,  or  the  outflow  can  be  cut  down  to  the 
inflow  and  a  layer  of  solution  kept  at  all  times  above  the  charge. 

The  solution  running  on  a  leaching  charge  to  some  extent 
presses  out  or  displaces  the  solution  or  moisture  below  it  and  to 
some  extent  dilutes  or  is  diluted  by  it.  Dilution  is  especially 
the  case  with  that  moisture  absorbed  by  the  ore  and  adhering  to 
and  wetting  the  grains,  such  as  is  in  evidence  when  the  charge  is 
drained.  While  that  filling  the  interstices  or  voids  between  the 
grains  when  the  charge  is  saturated,  and  which  is  less  closely  in 
contact  with  the  grains,  is  mainly  displaced  by  the  solution 
above  it  while  percolation  is  in  progress. 


PERCOLATION  101 

The  first  solution  having  been  run  on  top  of  a  well-drained 
charge,  in  the  course  of  a  little  while  the  dribbling  flow  from  the 
bottom  of  the  vat  commences  to  increase  as  a  result  of  the  dis- 
placed moisture  and  diluted  solution  reaching  the  bottom  of  the 
vat  as  the  advance  guard  of  the  solution  running  on  top  of  the 
charge.  This  flow  is  at  first  of  no  value,  being  mainly  displaced 
moisture  or  solution  in  which  the  cyanide  has  been  destroyed  by 
the  cyanicides  before  effecting  any  dissolution  of  gold  and  silver, 
but  gradually  accumulates  in  value.  This  value  may  be  in  a 
low  cyanide  strength  without  precious  metals  in  the  case  of  an 
ore  in  which  the  cyanicides  have  been  well  neutralized  but  the 
metals  are  slow  to  dissolve,  or  it  may  be  in  gold  and  silver  and  no 
cyanide  in  the  case  of  an  ore  still  containing  many  cyanicides, 
but  in  which  the  metal  dissolves  quickly  or  where  an  unprecipi- 
tated  solution  is  used  for  the  first  solution,  or  the  flow  may 
gradually  " build  up"  in  both  cyanide  and  the  precious  metals. 

The  operator  to  control  the  operations  of  a  plant  always  makes 
tests  of  this  solution  on  several  charges  at  the  starting  up  of  a 
new  plant,  and  occasionally  thereafter.  In  making  such  tests, 
as  soon  as  the  dribbling  flow  increases  substantially,  samples  of 
the  solution  are  taken  hourly  for  a  short  period,  then  every  two 
to  six  hours,  until  the  vat  is  finally  drained  for  discharging.  These 
solutions  are  tested  for  their  cyanide  strength,  acidity  or  pro- 
tective alkalinity,  and  gold  and  silver.  The  cyanide  strength 
and  protective  alkalinity  of  the  solutions  flowing  on  top  of  the 
charge  are  also  determined.  The  results  are  tabulated  for  com- 
parison and  may  easily  and  advantageously  be  plotted  to  show 
the  varying  cyanide  strength  and  precious-metal  content  during 
the  .different  periods.  These  results  indicate  when  the  outflow 
should  be  turned  from  waste  to  the  "  weak-gold  tank  "  as  con- 
taining gold  and  a  small  amount  of  cyanide;  when  to  turn  the 
flow  from  the  "  weak-gold  tank  "  into  the  "  strong-gold  tank  " 
in  the  effort  to  keep  the  strong  solution  as  high  in  cyanide  as 
possible  at  the  expense  of  the  weak  solution  and  thereby  save  in 
the  consumption  of  cyanide;  when  to  turn  back  from  the  strong 
to  the  weak-gold  tank;  and  finally  the  number  of  washes  that  it 
is  profitable  to  give  the  charges.  Correlatively  with  these  solu- 
tion samples  are  taken  samples  from  the  charge  every  few  hours 
during  the  period  in  which  it  is  supposed  the  gold  and  silver  are 
dissolving.  These  samples  are  immediately  washed  to  prevent 


102  TEXT  BOOK  OF  CYANIDE  PRACTICE 

the  quick  dissolution  which  takes  place  when  partly-treated  ore 
containing  cyanide  is  exposed  to  the  air,  and  which  would  lead 
to  wrong  conclusions.  The  samples  are  assayed  to  learn  the 
progress  of  the  dissolution  of  gold  and  silver,  and  the  length  of 
time  it  may  be  advisable  to  apply  strong  solution.  The  results 
may  be  tabulated  and  plotted  in  connection  with  those  obtained 
from  testing  the  outflowing  solution.  The  results  from  these 
samples,  through  the  amount  of  protective  alkalinity  shown  and 
its  variation  at  different  periods,  indicate  if  the  proper  amount 
of  lime  is  being  used.  Also  if  it  is  being  used  in  the  right  way  to 
give  a  constant  alkalinity,  or  should  its  alkaline  influence  be 
retarded  or  hastened. 

The  first  outflowing  solution  from  the  drain  cock  should  be 
allowed  to  flow  until  its  cyanide  strength  is  nearly  that  of  the 
solution  flowing  on  the  charge.  The  drain  cock  may  then  be 
closed,  and  the  solution  allowed  to  remain  in  contact  with  the 
ore  as  long  as  it  dissolves  gold  and  silver  at  an  active  rate.  This 
can  only  be  judged  from  the  assay  of  the  washed  samples  of  sand 
taken  at  different  times.  With  a  clean  gold  ore  containing  the 
gold  in  a  fine  state  of  division,  the  gold  may  be  dissolved  by  one 
contact  with  the  strong  solution  and  then  in  a  comparatively 
short  time.  With  gold  ores  containing  coarse  gold  or  with  much 
sulphide,  and  with  silver  ores,  a  point  is  reached  where  the  dis- 
solving action  of  the  solution  at  rest  with  the  ore  commences  to 
rapidly  fall,  owing  to  the  reducing  action  of  the  ore  and  cyani- 
cides  having  utilized  all  the  oxygen  and  destroyed  most  of  the 
cyanide,  the  dissolution  of  the  coarse  gold  causing  the  same  effect 
though  it  cannot  be  said  to  foul  the  solution.  The  solution 
should  now  be  drained  from  the  charge  that  fresh  and  active 
solution  may  be  placed  at  work.  It  is  preferable  to  draw  the 
solution  off  completely,  thereby  drawing  air  into  the  voids  or 
interstices  between  the  grains  which  were  formerly  occupied  by 
the  solution.  If  the  solution  still  in  contact  with  the  ore  is  not 
too  enervated  but  is  still  strong  in  cyanide,  a  rapid  dissolution 
of  gold  and  silver  takes  place.  When  the  solution  is  well  drained, 
the  drain  cock  may  be  closed  to  prevent  escape  of  the  air,  and 
strong  solution  again  flooded  over  the  charge.  As  the  solution 
sinks  in  the  charge  it  presses  out  the  air  which  rises  in  small 
bubbles  throughout  the  charge,  and  undoubtedly  has  some  help- 
ful effect  in  aerating  the  solution  and  charge.  After  the  charge 


PERCOLATION  103 

is  saturated  with  solution  and  the  bubbling  has  ceased,  the  drain 
cock  may  be  opened  and  thex  charge  started  leaching  with  solu- 
tion constantly  running  on  top  of  the  charge  to  an  amount  equal 
to  the  outflow.  Or  the  drain  cock  may  be  kept  closed  until  the 
solution  again  ceases  to  actively  dissolve  the  gold  and  silver, 
when  it  may  be  opened  for  draining  the  charge,  etc.;  but  it 
should  be  remembered  that  the  inflowing  solution  to  some  extent 
presses  down  and  displaces  the  moisture  that  still  remained  with 
the  ore  and  may  collect  it  in  the  bottom  of  the  vat,  which  would 
require  leaching  for  a  short  period  to  insure  fresh  solution  being 
brought  in  contact  with  the  bottom  of  the  charge. 

Instead  of  draining  the  charge  completely  before  adding  the 
second  solution,  the  second  solution  may  be  started  running  as 
soon  as  the  drain  cock  is  opened,  thus  causing  continuous  leach- 
ing without  aeration.  The  advisability  of  continuous  leaching 
or  of  alternate  leaching  and  aeration  varies  with  the  chemical 
and  physical  nature  of  the  ore  and  with  the  plant.  With  the 
metal  in  a  native  form,  continuous  leaching  with  a  freshly- 
aerated  solution  will  supply  enough  oxygen  to  give  a  high  ex- 
traction. With  a  sulphide  ore  the  aeration  and  oxidation  by 
exposing  the  charge  and  drawing  in  air  apparently  cracks  open 
the  sulphide  and  better  exposes  the  metal  for  dissolution,  thereby 
giving  a  higher  extraction,  as  well  as  oxidizing  the  ferrous  salts 
into  inert  ferric  oxide  and  the  alkaline  sulphides  into  thiocyanates 
or  sulphates,  reducing  the  consumption  of  cyanide  and  increasing 
the  dissolving  rate.  Alternate  periods  of  percolation  and  aera- 
tion or  intermittent  washing  require  more  time  than  continuous 
leaching,  but  the  volume  of  solution  required  to  give  a  thorough 
washing  is  smaller  on  the  same  principle  whereby  washing  by 
decantation  is  more  effective  with  a  precipitate  that  settles  to 
a  smaller  percentage  of  moisture.  The  thorough  drainings  also 
give  a  better  wash  on  a  charge  containing  slime,  or  poorly  filled, 
so  that  in  continuous  leaching  the  solution  following  the  line  of 
least  resistance  largely  shunts  by  portions  of  the  charge  with 
better  washings  of  other  parts.  Allowing  the  solution  to  remain 
at  rest  with  the  ore  permits  of  better  diffusion  of  the  rich  solution 
in  the  slime  agglomerates  and  pores  of  the  grains  of  ore  with 
the  solution  filling  the  larger  voids  between  the  grains,  and  by 
thoroughly  drawing  off  the  solution  must  better  draw  out  this 
sheltered  solution  for  subsequent  displacement  or  dilution. 


104  TEXT  BOOK  OF  CYANIDE  PRACTICE 

Some  information  as  to  the  necessity  of  aerating  the  charge 
can  be  obtained  by  examining  the  inflowing  and  outflowing 
solutions  for  their  reducing  power.  Besides  the  natural  drawing 
in  of  air  by  the  disappearing  and  outflowing  solution,  aeration 
may  also  be  obtained  by  using  a  vacuum  pump  connected  with 
the  leaching  vat  underneath  its  filter  bottom.  This,  besides 
drawing  the  solution  off  more  thoroughly,  draws  air  through  the 
charge,  thus  giving  a  very  thorough  aeration.  The  vacuum 
pump  method  was  introduced  at  a  time  when  sand  charges  con- 
tained much  slime,  for  the  purpose  of  increasing  the  leaching 
rate  and  giving  better  draining.  However,  it  was  found  to  pack 
the  charge  too  tightly  for  good  results  and  was  discarded,  except 
for  final  draining.  The  vacuum-pump  method  for  assisting  per- 
colation has  been  used  lately  with  reported  good  results,  and  it 
would  appear  that  it  might  work  well  on  a  charge  entirely  free 
from  slime.  The  best  method  of  giving  a  thorough  aeration  to  a 
charge  without  removing  it  from  the  vat,  consists  of  pumping 
air  underneath  the  filter  bottom  after  the  charge  is  drained  —  a 
reversal  of  the  vacuum-pump  method.  The  pressure  must  be 
low,  not  exceeding  5  pounds  per  square  inch  or  it  will  channel 
the  charge. 

It  is  a  problem  for  the  operator  of  each  plant  as  to  whether  the 
alternate  or  continuous  method  of  leaching  should  be  practiced. 
The  length  of  time  strong  or  standardized  solution  should  be 
applied  to  the  ore  is  indicated  by  the  time  it  takes  to  put  the  gold 
and  silver  in  solution,  but  not  absolutely.  The  value  in  a  gold 
ore  may  dissolve  in  24  hours,  but  require  two  additional  days 
for  washing  out.  If  75  per  cent  of  the  dissolvable  value  will  go 
into  solution  in  12  hours,  it  may  be  better  to  draw  the  strong 
solution  off  or  stop  its  use  at  that  time,  and  begin  washing  with 
a  weak  solution,  relying  upon  the  remaining  value  to  go  into 
solution  sufficiently  soon  during  the  time  of  using  and  washing 
with  weak  solution  to  get  the  maximum  extraction  and  yet  effect 
a  saving  in  the  consumption  of  cyanide,  for  the  use  of  a  strong 
solution  increases  the  costs  over  a  weak  solution  equally  effective 
or  effectively  used,  by  its  increased  activity  on  the  cyanicides 
and  the  zinc,  etc.  Again,  a  silver  ore  may  require  six  or  eight 
days  to  dissolve  the  metal,  while  the  final  washes  are  completed 
within  a  day  or  two  thereafter.  In  such  a  case  it  would  not  be 
advisable  to  stop  using  the  strong  solution  before  practically  all 


PERCOLATION  105 

the  dissolvable  metal  was  in  solution.  It  may  be  said  in  passing 
that  there  is  only  one  iron-clad  rule  regarding  the  amount,  time, 
and  strength  of  solution  to  be  used,  and  that  is  that  the  value 
shall  be  dissolved  and  washed  out  as  thoroughly  as  is  economi- 
cally practicable,  and  no  two  cyanide  operators  will  use  the  same 
exact  methods,  though  in  principle  there  is  no  important  difference. 

The  weak  solution  follows  the  strong  or  standardized  solution 
to  wash  out  the  dissolved  value  and  to  effect  part  of  the  final 
dissolution.  Having  determined  how  many  tons  of  solution  will 
be  standardized  up  to  the  maximum  dissolving  strength  each  day 
or  per  charge  in  the  usual  practice,  this  quantity  of  solution  is 
diverted  from  that  flowing  from  the  vats  when  at  its  strongest, 
the  balance  of  the  flow  going  into  the  weak  solution.  With 
plants  crushing  in  water,  the  amount  of  weak  solution  often 
increases  to  a  point  where  it  cannot  be  handled  or  utilized.  In 
such  cases  some  of  the  weakest  of  the  solution  is  run  to  waste 
after  passing  through  the  zinc  boxes.  The  weak  solution  is 
generally  applied  as  a  continuous  percolation  instead  of  inter- 
mittently. A  solution  is  always  applied  for  a  long  time  to  the 
surface  of  a  charge  before  its  characteristics  appear  in  the  out- 
flow; following  the  first  application  of  strong  solution  the  out- 
flow may  be  weak  in  cyanide  and  metal  for  a  long  period,  gradually 
building  up  and  continuing  high  in  both  long  after  the  change  to 
weak  solution,  which  gives  rise  to  the  saying  that  the  strong 
solution  dissolves  the  value  but  the  weak  solution  washes  it  out. 
This  tardiness,  besides  being  affected  by  the  cyanicides  and  dis- 
solving rapidity  of  the  ore,  is  increased  by  the  depth  of  the  charge 
and  its  slow  leaching  rate  due  to  slime  or  the  fineness  of  the  ore. 

The  final  water  washes  are  applied  after  the  weak  solution 
has  washed  nearly  all  the  dissolved  metal  out  of  the  ore.  The 
amount  of  water  used  is  just  sufficient  to  keep  the  volume  of 
solution  in  a  plant  constant.  A  plant  treating  ore  containing 
slime  filled  into  the  vats  dry  will  discharge  a  tailing  residue  con- 
taining 20  per  cent  or  more  of  moisture.  In  such  a  plant  a  vat 
containing  100  tons  of  ore  may  be  washed  with  25  tons  of  water, 
and  even  more  to  make  up  for  the  loss  by  leakage  and  evapora- 
tion. In  a  plant  treating  wet-filled  sand,  the  sand  will  probably 
drain  to  15  per  cent  moisture  before  the  cyanide  solution  is  applied, 
but  as  the  residue  is  discharged  with  the  same  amount  of  moisture, 
no  wash  water  can  be  used,  unless  owing  to  the  slow  dissolving 


106  TEXT  BOOK  OF  CYANIDE  PRACTICE 

rate  of  the  metal,  the  first  outflowing  solution  is  so  barren  in 
cyanide  and  metal  that  it  may  be  run  to  waste.  Sand  that  has 
been  crushed  in  cyanide  solution  and  wet-filled  into  the  vats  will 
be  discharged  with  probably  15  per  cent  moisture,  enabling  the 
use  on  a  100-ton  charge  of  ore  of  nearly  18  tons  of  wash  water, 
plus  the  loss  by  evaporation  and  by  the  large  leakage  incidental 
to  such  a  plant.  In  actual  practice  the  slime  plant  usually  re- 
quires more  than  its  proportion  of  wash  water,  or  dilutes  the  solu- 
tion in  circulation,  and  when  in  conjunction  with  a  sand  plant 
where  crushing  is  done  in  water  often  requires  weak  solution  to 
be  run  to  waste,  while  where  crushing  is  performed  in  solution, 
it  cuts  down  the  rightful  share  of  wash  water  of  the  sand  plant. 

Where  water  cannot  be  used  for  the  final  wash,  weak  solution 
performs  the  final  washing.  When  water  is  used,  the  wash  by 
weak  solution  is  theoretically  to  the  point  where  the  water  will 
just  complete  the  work.  As  it  is  not  practical  to  determine  this 
for  every  charge  by  assaying  the  outflowing  solution,  the  final 
weak-solution  washes  usually  take  the  dissolved  metals  out  pretty 
thoroughly,  while  the  water  wash  acts  as  the  factor  of  safety  and 
washes  out  the  final  cyanide.  To  wash_a_j£aching  ..charge  effi- 
ciently depends  mainly  upon  the  amount  of  solution  passed 
through  it  and  not  upon  the  length  of  time  occupied  in  washing, 
consequently  the  operator  determines  the  number  of  tons  of 
each  solution  he  wishes  to  be  applied,  which  is  generally  reduced 
fxT'a  certain  number  of  washes  of  so  many  tons  each.  SancN 
charges  are  generally  washed  until  the  final  solution  assays  at 
least  as  low  as  20  cents  per  ton  or  lower,  which  with  well-drained) 
residues  showing  15  per  cent  moisture  would  indicate  a  maximumj 
loss  of  3J  cents  per  ton  of  dry  sand,  while  the  actual  loss  woulc 
undoubtedly  be  much  lower.  If  _the__  final  washing  had  beer 
with  a  weak  KCN  solution  of  1 -pound  strength,  it  would  show  a 
loss  of  .18  pound  KCN  or  more  per  ton  of  dry  ore.  If  the  fina 
washing  was  with  water  and  the  outflow  titrated  1  pound  KCN 
it  would  indicate  a  maximum  mechanical  loss  of  much  less  than 
.18  pound  per  ton,  for  undoubtedly  the  strong  solution  is  nearly 
all  found  at  the  bottom  of  the  charge,  and  the  same  principle 
holds  true  with  reference  to  the  dissolved  gold  and  silver  still 
remaining. 

The  tank  is  sampled  for  assay  after  draining.     For  test  pur- 
poses a  sample  of  the  well-mixed  sand  may  be  at  once  washed  by 


PERCOLATION  107 

decantation  or  otherwise  to  be  assayed  as  a  "  washed  sample." 
The  difference  between  the  washed  and  the  unwashed  sample 
shows  the  amount  of  dissolved  value  lost  through  poor  washing 
of  the  charge.  The  amount  of  KCN  and  dissolved  gold  and 
silver  mechanicaHy~IosT~by ""t>eing  discharged  in  the  residue  may 
^alsoTbe  obtained  by  taking  300  grams  of  the  residue,  adding 
^water"  sufficient  to  make  a  one  to  one  solution,  —  estimating  the 
moisture  or  determining  it  in  another  part  of  the  sample,  —  agi- 
tating for  several  minutes  and  drawing  off  and  testing  any  aliquot 
part.  Thus  if  300  grams  of  residue  containing  20  per  cent  of 
moisture  are  taken,  it  is  equivalent  to  240  grams  of  dry  sand  and 
60  c.c.  of  water,  to  which  180  c.c.  of  water  should  be  added  to 
give  a  one.  to  one  solution.  If  120  c.c.  of  the  solution  is  used  for 
assay,  it  will  represent  that  metal  held  in  120  grams  dry  pulp 
(practically  4  assay  tons),  while  the  titration  of  10  c.c.  will 
give  the  pounds  of  KCN  mechanically  lost  per  ton  of  dry  pulp. 
Samples  should  be  taken  on  test  charges  representing  different 
depths  of  the  sand  charge,  for  it  is  sometimes  found  that  the 
metal  is  not  as  thoroughly  dissolved  in  the  lower  part  of  the 
charge,  due  to  the  lack  of  aeration  and  possibly  the  weakened 
condition  of  the  strong  solution  reaching  that  part  of  the  charge. 
The  bottom  of  the  charge  contains  more  moisture  due  to  its 
packed  condition  preventing  free  draining,  and  to  the  tendency 
of  the  moisture  just  above  the  filter  bottom  to  be  retained  in  the 
sand  by  a  species  of  surface  tension,  while  this  lower  moisture 
must  be  much  richer  than  that  above. 


CHAPTER  IX 

SLIME   TREATMENT   AND   AGITATION 

Definition  of  Slime.  —  Solids  may  be  said  to  exist  in  two 
forms,  crystalline  and  amorphous.  Substances  in  a  crystalline 
form  have  a  definite  and  regular  shape;  they  are  compact  and 
substantially  solid.  Grains,  crystals,  and  solid  bodies  represent 
the  crystalline  structure.  The  amorphous  is  the  opposite  of  the 
crystalline  structure;  it  is  irregular  and  indeterminate  in  shape, 
and  less  compact  and  substantial  than  the  crystalline.  In  the 
cyanide  process  the  crystalline  is  represented  by  "  sand  "  and  the 
amorphous  by  "  slime."  Sand  may  be  said  to  be  that  part  of 
the  ore,  however  fine  it  may  be,  which  is  crystalline,  granular, 
sharp,  clean,  compact,  and  under  the  microscope  presents  reg- 
ular structure,  sharp  edges,  and  solid  faces;  which  readily  settles 
in  still  water  and  does  not  muddy  water,  and  which  can  be 
leached.  While  slime  may  be  said  to  be  noncrystalline,  light, 
feathery,  flaky,  non compact,  impalpable  material,  showing  irreg- 
ular shape  and  structure;  which  muddies  water  and  does  not 
readily  settle  in  still  water,  but  remains  in  suspension  dissemi- 
nated throughout  the  water,  to  gradually  agglomerate  and  settle 
as  a  flocculent  slime  to  form  a  plastic  clay  or  mud,  very  unleach- 
able  and  impermeable  by  water.  Slime  is  sometimes  spoken  of 
as  a  "  colloid,"  a  term  applied  to  substances  suspended  in  solu- 
tion in  a  semisolid  state. 

While  sand  partakes  of  the  nature  of  quartz,  slime  partakes  of 
the  nature  of  clay.  Slime  is  usually  a  silicate  of  aluminum, 
iron,  or  alkaline  earths.  The  hydrated  aluminum  silicate, 
kaolin  (A1203.2  SiO2.2  H2O),  is  a  most  prominent  slime  or  con- 
stituent of  the  slimes,  and  shows  that  the  term  "  colloid  hydrate  " 
is  not  a  misnomer  as  a  technical  term  for  slime.  Slime  is  found 
least  in  hard,  crystalline  quartz,  and  most  in  talcose,  clayey, 
feldspathic,  and  oxidized  ores,  or  those  containing  kaolin,  alunite, 
and  limonite.  The  percentage  increases  with  finer  crushing  as 
the  amount  of  impalpable  powder  produced  must  necessarily 

108 


SLIME  TREATMENT  AND  AGITATION          109 

increase.  The  slime  produced  in  crushing  a  hard  quartz  probably 
has  certain  crystalline  qualities  to  account  for  its  quicker  settling 
and  more  permeable  nature  than  that  arising  from  a  clayey  ore, 
for  a  slime  resulting  from  a  quartzose  ore  can  be  settled  or  fil- 
tered much  easier  than  that  from  a  clayey  ore.  Flocculent 
slime  undoubtedly  carries  considerable  fine  sand  covered  and 
held  in  suspension  by  a  coating  of  slime  or  colloidal  material. 

Slime  is  sometimes  defined  without  reference  to  the  crystalline 
or  amorphous  qualities,  as  that  part  of  the  ore  which  will  pass  a 
200-mesh  screen.  This  interpretation  has  been  given  the  term 
because  it  is  generally  considered  by  many  that  material  finer 
than  200-mesh  had  best  be  treated  in  the  slime  plant,  even  though 
it  contains  grains  that  are  leachable,  also  because  material  ground 
to  200-mesh  is  excellent  to  treat  in  a  slime  plant.  The  use  of 
the  term  slime  in  this  manner  has  rendered  it  necessary  in  refer- 
ring to  an  amorphous  slime  as  discussed  in  the  preceding  para- 
graphs to  use  the  terms  "  flocculent  slime,"  "  clay  slime,"  ''  col- 
loid slime,"  or  "  true  slime."  It  would  be  well  to  distinguish  a 
granular  slime  passing  a  200-mesh  by  some  modifying  term,  as 
a  "  sandy  slime/'  reserving  the  word  "  slime  "  for  the  amorphous 
and  real  slime,  but  using  the  term  "  true  slime  "  or  other  until 
the  present  confusion  in  the  use  of  the  word  "  slime  "  has  passed 
away.  It  is  highly  necessary  to  distinguish  between  a  sandy 
slime  and  a  true  slime  as  some  processes,  agitating  machinery, 
and  filters  may  be  wholly  or  better  adapted  for  treating  the  one 
class  of  material  than  the  other.  This  is  owing  to  the  plasticity 
and  the  impermeability  by  water  of  a  true  slime,  which  as  granu- 
lar material  is  added  and  it  becomes  sandier,  becomes  less  plastic 
and  more  permeable  and  leachable,  and  in  part  settles  faster. 
Also  because  a  sandy  slime  settles  to  a  denser,  more  compact 
sludge  that  is  harder  to  move  and  disintegrate. 

Dehydrating  or  removing  the  moisture  from  a  slime  by  heat- 
ing or  roasting  renders  it  more  susceptible  to  leaching  and  less 
adsorptive  of  moisture  which  cannot  be  displaced,  a  fact  that 
has  weight  when  the  roasting  of  dry-crushed  ore  is  being  con- 
sidered. 

Slime  Settlement.  —  The  addition  of  any  one  of  various  acids, 
alkalis,  or  neutral  salts  to  water  containing  slime  in  suspension 
causes  the  suspended  matter  to  coagulate  and  settle  much  faster 
and  to  a  smaller  bulk  than  naturally.  Lime  is  the  only  substance 


110  TEXT  BOOK  OF  CYANIDE  PRACTICE 

added  for  settling  purposes  in  the  cyanide  process.  Some  idea 
of  the  amount  of  lime  required  can  be  obtained  by  laboratory 
tests  on  average  samples  of  the  slime  pulp  placed  in  graduates, 
to  which  known  quantities  of  lime  are  added,  and  the  subsidence 
compared  at  different  periods  of  time.  However,  the  amount 
used  in  actual  practice  is  determined  by  that  which  gives  the 
quickest  settling  into  the  least  bulk  with  an  economical  amount 
of  lime.  Too  much  lime  may  retard  the  settling.  The  amount 
of  lime  used  is  variable,  in  some  plants  a  few  pounds  per  ton  of 
dry  slime  will  suffice;  in  others  as  much  as  10  or  20  pounds  of 
lime  has  been  used  per  ton  of  ore. 

The  settlement  of  slime  by  lime  or  other  alkali,  an  acid,  or  a 
neutral  salt  is  on  the  theory  that  particles  of  any  kind  when 
suspended  in  a  liquid  are  electrostatically  charged.  That  these 
charges  while  they  may  be  positive  or  negative  for  different 
kinds  of  suspended  matter,  are  still  of  the  same  sign  for  all  parti- 
cles of  the  same  substance,  and  consequently  repel  each  other, 
for  two  different  substances  in  contact  have  equal  and  opposite 
electrostatic  charges  at  their  contact  surfaces.  The  tiny  slime 
particles  by  the  repulsion  of  their  like  electrostatic  charges 
together  with  their  relatively  large  surface  in  proportion  to  their 
weight  and  their  solubility  or  saturation  similar  to  that  of  a 
sponge  suspended  in  water,  counterbalance  the  action  of  gravity 
and  remain  suspended  in  the  water.  In  short,  their  density 
differs  so  little  from  that  of  the  surrounding  liquid  that  they 
remain  in  suspension  or  settle  at  an  infinitesimally  slow  rate. 
Heating  the  water  lightens  its  density  and  lessens  its  viscosity 
and  confers  greater  mobility  so  that  the  particles  may  better 
settle  through  their  higher  specific  gravity,  but  on  a  working 
scale  the  cost  of  heating  overbalances  the  advantage  of  the 
quicker  settling.  The  introduction  of  an  acid,  alkali,  or  salt 
capable  of  disassociating  produces  both  positively  and  negatively- 
charged  ions  which  attract  the  slime  particles  having  different 
charges,  causing  a  coagulation  of  the  slime  to  expose  less  surface 
for  a  given  mass  and  consequently  to  better  settle.  Substances 
used  for  connecting  other  substances  in  this  way  by  their  electro- 
static charges  are  termed  electrolytes;  thus  lime  is  an  electrolyte 
in  the  settling  of  slime  by  its  aid. 

The  settling  rate  decreases  with  the  density  or  viscosity  of  the 
pulp.     With  a  very  dilute  pulp  the  slime  at  first  settles  rapidly 


SLIME  TREATMENT  AND  AGITATION          111 

to  leave  a  clear  solution,  but  the  settling  rate,  the  downward 
movement  of  the  line  of  demarcation  between  the  slime  pulp  and 
the  clear. solution,  gradually  grows  less  as  the  underlying  slime 
pulp  becomes  thicker  and  denser  until  the  settling  rate  practi- 
cally becomes  nil.  In  this  movement  the  true  slime  appears  to 
move  downward  by  layers,  that  slime  at  the  top  of  the  charge 
when  settling  was  started  becoming  the  top  of  the  settled  slime. 
While  the  settling  rate  is  thus  decreased  through  the  settling  of 
the  slime  being  retarded  by  the  density  or  increasing  density  of 
the  medium  through  which  it  is  settling,  in  a  practical  way  the 
depth  of  the  settling  column  has  a  most  important  influence. 
It  is  apparent  that  the  slime  particles  in  a  charge  4  feet  deep  in  a 
small-diameter  tank  will  have  to  settle  through  practically  four 
times  the  distance  as  in  the  same  charge  when  1  foot  deep  in  a 
large-diameter  tank  of  four  times  the  area,  and  that  there  is  a 
greater  retardation  in  the  4-foot  charge  owing  to  the  greater 
weight  of  solution  or  solution  and  pulp  overlying  any  section  of 
the  depth  and  thus  making  the  density  greater.  This  will  ex- 
plain why  shallow  tanks  of  large  diameter  are  necessary  in  de- 
canting, instead  of  deep  tanks  of  small  diameter. 

Classification  or  Separation  of  Sand  and  Slime.  —  Slime  treat- 
ment may  refer  to  the  treatment  of  a  true  slime,  of  a  sandy  slime 
containing  the  finer  sand  made  in  crushing  together  with  the  true 
slime,  or  of  all  the  ore  ground  fine  —  a  case  of  "  all-sliming." 
The  methods  used  in  treating  these  three  classes  of  material  do 
not  vary  in  the  main,  though  the  presence  or  absence  of  sand  is  an 
important  detail.  Where  the  decantation  system  of  treatment  is 
used,  it  is  aimed  to  treat  only  the  true  slime,  on  account  of  the 
greater  ease  with  which  the  sand  can  be  treated  in  a  leaching  plant 
and  the  higher  efficiency  of  the  leaching  plant  in  washing  out  the 
dissolved  value.  With  a  modern  filter  plant  it  is,  with  most 
filters,  desirable  to  treat  all  or  a  part  of  the  sand  with  the 
slime,  since  they  can  handle  a  sandy  slime  better  than  a  true 
slime. 

For  producing  a  true  slime  and  furnishing  a  clean  sand  at 
the  same  time,  the  Dorr  classifier  is  the  only  machine  approach- 
ing perfection.  Where  it  is  necessary  to  throw  the  finer  sand 
into  the  slime,  cone  classifiers  may  be  used,  or  the  Dorr  clas- 
sifier modified  so  as  to  produce  a  sandy  slime.  Cone  classifiers 
never  give  an  absolutely  slime-free  sand  for  the  leaching  plant, 


112  TEXT  BOOK  OF  CYANIDE  PRACTICE 

consequently  their  underflow  of  coarse  sand  should  be  reclassi- 
fied  in  a  Dorr  machine. 

Pulp  Thickening.  —  The  slime  pulp  runs  from  the  classifiers 
to  pulp  thickeners.  These  are  of  two  kinds:  those  operating  on 
the  settling  principle  with  cone  bottoms  discharging  a  thickened 
pulp,  and  those  using  the  same  settling  principle,  but  discharging 
the  settled  slime  by  some  mechanical  means.  Lime  is  usually 
added  to  the  slime  flow  before  entering  the  thickeners  for  neu- 
tralizing the  acidity  and  to  effect  quicker  settling.  The  pulp 


EED  LAUNDER1, 


CLEAR 
SOLUTION 
DISCHARGE 


Fig.  7.  — The  Dorr  Slime  Thickener. 

flow  is  conducted  to  the  center  of  the  tank  or  cone  and  introduced 
into  it  through  a  central  pipe  emptying  a  few  feet  below  the  sur- 
face of  the  water.  In  this  way  the  slime  flow  does  not  disturb 
the  water  and  settling  slime,  but  emits  from  the  bottom  of  the 
pipe  and  rises  and  moves  at  a  very  slow  rate  of  speed,  under  con- 
ditions favorable  for  the  deposition  of  the  slime  material,  to 
overflow  the  side  or  rim  of  the  cone  or  tank  as  a  clear  or  partly 
clarified  solution  or  water  ready  to  be  reused  or  run  to  waste. 
From  the  bottom  of  the  tank,  the  thickened  sludge  may  be 
drawn  off  continuously,  or  intermittently  with  more  or  less 
trouble,  with  a  dilution  that  is  variable  but  seldom  less  than  one 
part  of  solution  or  water  to  one  part  of  dry  slime. 


SLIME  TREATMENT  AND  AGITATION         113 


Charging  for  Agitation.  —  The  pulp  is  drawn  continuously  or 
intermittently  into  the  agitation  tank,  or  the  slime  flow  may  be 
settled  in  an  agitation  or  collecting  tank  in  a  way  similar  to  that  in 
the  pulp  thickeners.  After  the  agitator  has  received  its  charge, 
lime  may  be  added  as  a  milk-of-lime,  also  sufficient  cyanide,  by 
being  dissolved  in  a  small  stream  of  solution,  to  bring  the  lime 
and  cyanide  strength  up  to  the  desired  amount.  Lead  acetate 


Fig.  8.  —  The  Hendryx  Slime  Thickener  or  Tailing  Dewaterer. 

dissolved  in  water  may  also  be  added  for  the  purpose  of  precipi- 
tating any  alkaline  sulphides  which  may  form.  Any  extra  solu- 
tion to  bring  the  charge  to  the  desired  proportion  of  solution  and 
dry  pulp  is  added.  If  the  crushing  has  been  done  in  solution, 
the  pulp  thickeners  may  only  be  required  to  reduce  the  pulp  to 
the  consistence  desired  for  agitation,  so  that  no  additional  solu- 
tion need  be  added.  But  if  crushing  is  done  in  water,  the  pulp 
thickeners  are  worked  to  their  highest  efficiency  or  the  pulp  in  the 
collecting  or  combined  collecting  and  agitating  tank  is  allowed  to 
settle,  and  as  much  water  decanted  off  as  is  possible  before  adding 
cyanide  solution  and  beginning  agitation.  With  a  plant  crush- 


114  TEXT  BOOK  OF  CYANIDE  PRACTICE 

ing  in  water,  it  is  necessary  to  dewater  the  pulp  to  the  lowest 
possible  percentage  of  moisture,  or  the  amount  of  solution  in  the 
plant  will  soon  increase  to  such  a  quantity  that  some  of  it  must 
be  run  to  waste. 

Amount  of  Solution  in  Agitation.  —  Slime  is  agitated  with 
varying  amounts  of  solution.  Where  decantation  is  practiced, 
1  part  of  dry  slime  will  be  agitated  with  from  3J  to  6  parts  of 
solution,  that  a  large  volume  of  solution  may  be  decanted  off  to 
enable  a  low  tailing  to  be  obtained.  Where  the  slime  is  filtered 
without  decantation  it  will  be  kept  much  thicker,  perhaps  as 
much  as  1  part  of  dry  pulp  to  1.2  parts  of  solution  (by  weight). 
The  density  of  the  pulp  or  the  proportion  of  solution  to  dry  pulp 
has  an  important  influence  on  the  dissolution  of  gold  and  silver, 
even  though  the  strength  of  the  solution  be  the  same.  The  dis- 
solution of  the  gold  and  silver  will  be  slower  with  a  thicker  pulp. 
A  pulp  of  3  parts  of  solution  to  1  of  ore  against  one  containing 
only  1J  parts  of  solution  brings  double  the  amount  of  cyanide 
and  dissolved  oxygen  into  play,  consequently  with  a  thin  pulp 
the  strength  of  solution  can  be  kept  lower,  while  with  the  same 
strength  the  dissolving  rate  will  be  faster.  In  both  agitation  and 
percolation,  so  far  as  concerns  the  dissolving  of  the  metal,  the 
effect  of  a  strong  solution  small  in  quantity  and  applied  for  a 
short  time  can  be  equaled  by  a  weaker  solution  larger  in  quantity 
and  applied  for  a  greater  length  of  time.  A  thin  pulp  is  often 
agitated  and  then  settled  and  decanted  from  to  a  thicker  con- 
sistence before  being  filtered,  in  the  effort  to  meet  the  above 
conditions  and  to  reduce  the  value  per  ton  of  the  solution  re- 
maining in  the  pulp  to  be  filtered.  With  air  agitation  there  is 
no  question  but  that  a  good  aeration  is  obtained,  but  with  me- 
chanical agitators  the  necessity  of  aeration  and  the  action  of 
reducers  in  the  pulp  should  be  examined.  It  has  been  noted  in 
many  cases  that  after  a  certain  length  of  agitation,  no  more 
value  would  go  into  solution,  but  by  removing  the  old  solution 
and  applying  new,  either  by  decantation  or  the  short  contact 
with  wash  solution  during  the  filtering  process,  the  remaining 
dissolvable  value  goes  into  solution  quickly.  The  same  results 
on  the  aeration  of  a  charge  and  adding  newly  aerated  and  pre- 
cipitated solution  has  been  noticed  in  the  leaching  process. 

Strength  of  Solution  and  Time  Required  in  Agitation.  —  The 
strength  of  solution  that  it  is  advisable  to  use  will  vary  with  the 


SLIME  TREATMENT  AND  AGITATION         115 

(nature  of  the  ore  and  the  volume  of  solution  used.  On  gold  ore 
a  strength  of  .05  per  cent  (Impound)  to  .1  per  cent  (2  pounds)  is 
generally  sufficient,  on  silver  ores  up  to  .4  per  cent  (8  pounds), 
and  on  gold  concentrate  up  to  .5  (10  pounds).  In  some  few  cases 
a  .025  per  cent  (i  pound)  solution  is  sufficient  on  gold  o^es  when 
using  a  large  volume  of  solution  and  a  long  contact.  Some  gold 
ores  contain  the  metal  in  such  a  fine  state  that  when  crushing  in 
solution  and  all  sliming  —  crushing  all  the  ore  to  a  sandy  slime 
—  nearly  all  the  gold  will  be  in  solution  by  the  time  the  tube 
mill  is  passed.  But  in  most  cases  an  agitation  of  3  to  18  hours 
is  required  with  gold  ores,  up  to  a  few  days  with  silver  ores,  and 
up  to  10  days  with  concentrate.  The  progress  of  the  dissolution 
of  the  metals  and  the  consumption  of  cyanide  and  lime  should  be 
frequently  tested  by  taking  samples  of  the  charge,  testing  and 
assaying  the  filtered  solution,  and  assaying  the  washed  pulp. 
The  results  may  be  tabulated  and  plotted  and  filed  for  compari- 
son with  others.  The  solution  during  agitation  may  be  tested 
for  its  reducing  power  and  the  alkaline  sulphides  formed. 

Intermittent  and  Continuous  Agitation.  —  It  is  not  necessary 
to  completely  dissolve  the  gold  and  silver  at  the  first  agitation 
where  decantation  is  practiced,  especially  if  the  dissolving  rate 
becomes  slow  during  the  latter  part  of  the  period  of  agitation. 
The  agitations  following,  for  the  purpose  of  mixing  the  solution 
with  the  pulp,  can  be  relied  upon  to  effect  final  dissolution, 
together  with  the  long-continued  contact  between  the  .ore  and 
the  solution  that  takes  place  in  the  decantation  process.  "Where 
the  pulp  is  to  be  filtered,  the  value  should  be  dissolved  in  one 
agitation  unless,  on  account  of  the  action  of  reducers  and  the 
fouling  of  the  solution  toward  further  dissolving  of  the  precious 
metals,  it  is  necessary  to  use  fresh  solution;  though  this  can 
probably  be  met  by  aeration,  at  least  the  cause  should  be  investi- 
gated and  studied. 

Two  methods  of  agitation  are  in  use.  The  charge,  intermit- 
tent, or  single-agitation  system,  treating  each  charge  separately 
and  individually,  which  was  formerly  used  entirely;  and  the  con- 
tinuous system  more  recently  developed.  In  the  continuous  sys- 
tem the  charge  is  delivered  continuously  to  the  first  of  a  series  or 
battery  of  agitation  tanks,  through  which  the  pulp  passes  to  be 
delivered  from  the  last  agitator  in  the  series  to  a  filter  or  a  stock 
tank  supplying  a  filter.  The  method  is  illustrated  in  Fig.  9. 


116 


TEXT  BOOK  OF   CYANIDE  PRACTICE 


The  pulp  flows  from  pulp  thickeners  which  settle  the  slime  to 
the  proper  dilution  or  consistence,  through  the  launder  A  to  the 
first  of  the  tanks  —  which  are  the  Pachuca  or  Brown  air-agitator 
type.  Here  it  is  drawn  to  the  bottom  of  the  tank  to  rise  to  the 
top  through  the  central  column  and  again  descend  to  the  bottom, 
in  the  process  of  being  circulated  up  through  the  central  column 
and  down  outside  of  it.  The  iron  pipe  B,  whose  inlet  end  is  at 
least  a  few  feet  below  the  discharge  of  the  central  column  of  the 
agitator  and  about  midway  between  the  column  and  the  outside 
of  the  tank,  and  which  is  set  on  an  angle  of  60  degrees,  discharges 


Fig.  9.  —  Continuous  Agitation  System. 

into  the  next  tank  at  a  point  midway  between  the  column  and 
the  outside  of  the  tank.  In  this  way  the  pulp  introduced  at  A  is 
agitated  in  each  tank  and  flows  through  the  series  to  be  dis- 
charged at  C.  The  advantage  of  this  system  is  that  the  large 
amount  of  labor,  worry,  wear  and  tear,  and  loss  of  time  involved 
in  charging  and  discharging  a  tank  is  entirely  avoided.  With 
well  regulated  tanks  and  equipment,  attention  need  only  be 
given  to  keeping  the  machinery  in  order  and  a  watch  over  opera- 
tions. The  gain  in  mill  height  or  the  elimination  of  the  costly 
item  of  lifting  the  pulp  to  a  higher  level  is  an  important  item  in 
this  system.  In  the  charge  system  with  the  regulation  Pachuca 
tank,  the  pulp  will  be  discharged  at  D  which  is  45  feet  below  the 
top  of  the  tank.  With  the  continuous  system  the  discharge  is  at 


SLIME  TREATMENT  AND  AGITATION         117 

Cj  which  is  only  a  few  feet  below  the  top  of  the  tank.  A  longer 
agitation  is  given  the  pulp,  for  with  the  charge  system  from  J  to 
J  of  the  time  is  occupied  in  filling  and  discharging  the  tank, 
whereas  in  the  continuous  system  the  tank  is  agitating  all  the 
time  except  when  it  is  desired  to  work  on  or  repair  a  tank,  which 
can  be  done  by  cutting  it  out  of  the  series  through  pipes  and 
valves  connecting  the  tank  to  tank  discharges,  the  pulp  in  the 
tank  to  be  worked  upon  being  drawn  off  from  the  bottom  of  the 
tank.  If  the  filter  or  filter-stock  tank  is  placed  just  underneath 
the  discharge  from  the  last  tank,  an  emergency  pump  should  be 
provided  to  lift  the  pulp  from  the  bottom  discharges  of  the  tanks. 

The  success  of  the  continuous  system  primarily  depends  on 
the  pulp  being  homogeneous  in  all  the  tanks  ;  which  has  been 
proven  to  be  the  case  with  Pachuca  tanks  through  sizing  tests 
made  of  samples  taken  from  the  different  tanks  ;  though  in  some 
cases  with  a  pulp  containing  coarse  sand  it  may  require  consid- 
erable experimenting  in  the  arrangement  of  the  connecting  pipes 
to  get  the  pulp  homogeneous  in  all  the  tanks.  And  secondly, 
that  no  particle  of  pulp  shall  move  faster  than  others  through 
the  series  and  be  discharged  with  less  than  the  proper  amount 
of  agitation.  That  there  must  be  a  tendency  to  do  this  can 
easily  be  seen,  but  a  particle  of  pulp  that  is  undertreated  in  one 
tank,  by  passing  out  before  receiving  its  share  of  agitation, -on 
entering  the  next  tank  is  placed  on  an  equal  footing  with  all 
particles  entering  the  tank  at  that  time.  Consequently  the 
probability  of  evil  results  due  to  a  particle  of  pulp  being  shunted 
across  the  series  of  tanks  and  discharged  without  the  proper 
amount  of  agitation  becomes  less  as  the  number  of  tanks  is 
increased.  By  using  the  same  number  of  agitating  tanks  in  the 
continuous  system  as  would  be  required  in  the  charge  system, 
the  use  of  a  number  of  tanks  together  with  the  extra  agitation 
due  to  no  loss  of  time  through  filling  and  discharging  —  which 
acts  as  a  factor  of  safety  —  the  same  extraction  ought  to  be 
secured  as  with  the  charge  system,  while  actual  working  results 
have  shown  a  higher  dissolution  due  to  the  more  prolonged 
agitation.  Even  if  a  lower  dissolution  was  obtained,  the  saving 
in  labor  and  other  costs  by  the  continuous  system  would  in  most 
cases  overbalance  the  lower  extraction. 

It  has  been  proposed  to  employ  a  single,  continuous-treatment 
tank  by  using  the  Just  silica-sponge  brick  bottom.  These  pre- 


118  TEXT  BOOK  OF  CYANIDE  PRACTICE 

pared  bricks  are  used  just  as  a  filter  cloth  in  a  leaching  vat,  by 
being  laid  and  held  in  a  steel  frame  to  act  as  a  false  or  filtering 
bottom.  The  bricks  are  so  porous  that  by  introducing  air  at  a 
low  pressure  underneath  the  false  bottom,  it  will  pass  through 
the  bricks  to  emerge  in  tiny  streams  that  will  keep  the  slime  in 
agitation.  Its  adaptation  to  the  continuous-agitation  system 
consists  in  using  a  rectangular  tank  somewhat  similar  to  a  zinc 
box  with  a  series  of  compartments  having  an  upward  and  down- 
ward flow,  all  compartments  being  of  the  same  length.  The 
pulp  as  it  flows  through  this  large  box  would  be  agitated  by  the 
air  passing  through  the  brick  bottom,  while  the  number  of  com- 
partments may  be  many  to  lessen  the  tendency  for  any  of  the 
particles  of  pulp  to  get  less  than  their  proper  share  of  agitation. 
The  successful  use  of  the  silica-sponge  brick  in  this  manner 
would  allow  an  agitator  to  be  built  and  worked  at  a  reasonable 
cost,  to  be  economical  of  space,  and  which  could  be  used  as  a 
filter-stock  tank  or  with  a  variable  amount  of  pulp,  for  which 
the  Pachuca  air-agitating  tank  is  not  adapted,  since  it  must  have 
a  certain  amount  of  pulp  or  the  air-lift  principle  will  not  cause 
the  pulp  to  circulate  and  agitate. 

The  perfection  of  the  continuous  system  has  advanced  the 
cyanide  process  to  a  point  where  the  ore  may  flow  in  a  continu- 
ous stream  from  the  ore  bin  to  the  tailing  dump  without  any 
intermittent  operations.  With  the  perfection  of  a  continuous 
filter  that  with  all  classes  of  pulp  will  cheaply  and  thoroughly 
wash  out  the  dissolved  metal,  even  with  rich  pulp,  and  that  will 
reduce  the  cyanide  mechanically  lost  to  a  relatively  small  amount, 
together  with  a  determination  of  the  simplest  and  most  eco- 
nomically efficient  agitator  for  continuous  agitation,  the  day  of 
percolation  will  be  passed  and  cyanide  plants  and  processes 
will  tend  to  become  as  standard  in  design  as  the  stamp-mill 
process. 

Types  of  Agitators.  —  The  first  style  of  agitator  that  was 
employed,  and  which  has  been  generally  used  with  the  decanta- 
tion  process,  is  the  mechanical  or  stir  agitator.  These  consist 
of  large,  round,  flat-bottomed  tanks  as  much  as  40  feet  in  diameter 
and  20  feet  deep.  They  are  equipped  with  stirring  blades 
attached  to  a  shaft  actuated  by  a  gear  mounted  over  the  tank  or 
underneath,  and  passing  up  through  the  bottom.  Agitation  of 
charges  containing  only  true  slime  by  these  agitators  is  not 


SLIME  TREATMENT  AND  AGITATION         119 

difficult,  especially  if  the  pulp  is  dilute,  but  as  the  amount  of 
sand  in  the  charge  increases,  ttie  difficulty  in  agitating  becomes 
greater.  This  is  owing  to  the  tendency  of  the  sand  to  pack  and 
to  resist  the  movement  of  the  blades,  which  results  in  increased 
power  being  required,  great  trouble  in  starting  a  settled  charge, 
and  severe  wear  and  tear  on  the  machinery.  The  stirring  gear 
in  some  types  may  be  started  with  the  arms  raised  and  in  the 
upper  and  more  dilute  portion  of  the  charge,  to  be  gradually 
lowered  as  the  charge  responds  to  the  agitation  and  loosens  up. 
Tanks  without  facilities  for  raising  or  lowering  the  blades  should 
have  them  set  2  feet  above  the  bottom  of  the  tank  to  enable  them 
to  be  easily  started,  as  the  sand  then  settles  below  them  and  yet 
can  be  brought  into  agitation  when  using  a  speed  of  500  to  800 
feet  per  minute.  Short  chains  and  iron  cables  have  sometimes 
been  hung  from  the  arms  to  assist  in  stirring  the  slime  below. 
Baffle  plates  may  be  attached  to  the  sides  of  the  tanks  to  insure 
better  mixing.  Two  sets  of  arms,  one  near  the  bottom  of  the 
tank  and  the  other  near  the  center  are  excellent.  Air  may  be 
pumped  through  perforated  pipes  in  the  bottom  of  the  tank  or 
through  pipes  attached  to  the  arms,  to  assist  in  the  agitation  and 
to  aerate  as  well.  Agitation  is  often  further  assisted  by  centrif- 
ugal pumps  taking  the  pulp  from  the  bottom  of  the  tank  and 
returning  it  to  the  top  of  the  charge. 

The  mechanical  or  stir  agitators  have  been  comparatively 
costly  in  the  horse  power  and  repairs  required,  and  the  agitation 
has  been  far  from  perfect.  Yet  the  facts  that  the  tanks,  being 
large  in  diameter  and  rather  shallow,  were  well  adapted  for  slime 
settling  and  for  decantation,  and  that  the  arm  stirs  were  excellent 
for  repulping  the  settled  slime  with  the  fresh  solution  added,  is 
the  reason  for  their  extensive  use  in  the  past.  The  thinness  of  the 
slime  agitated  in  working  with  the  decantation  process  —  3J  to 
6  parts  of  solution  to  1  of  dry  slime — has  assisted  them  to  do  good 
work.  Likewise  the  treating  of  all  the  sand  in  the  leaching  plant 
and  all  the  true  slime  in  the  slime  plant,  so  far  as  the  classifying 
apparatus  enabled  this,  as  is  always  the  case  with  plants  treating 
the  slime  by  decantation.  The  new  plants  being  built  are  all 
equipped  with  some  form  of  slime  filter,  consequently  mechanical 
or  stir  agitating  tanks  are  seldom  installed  now,  except  as  stock 
tanks  to  hold  and  keep  in  agitation  the  pulp  to  be  supplied  to 
the  filters.  They  are  well  adapted  for  this,  since  they  do  not 


120 


TEXT  BOOK  OF  CYANIDE  PRACTICE 


have  to  be  kept  full  or  nearly  full,  as  is  the  case  with  air  and 
some  of  the  other  agitators. 

Agitation  by  a  centrifugal  pump  drawing  from  the  bottom  of 
the  tank,  usually  a  conical-bottom  tank,  and  pumping  to  the  top 
of  the  tank,  has  been  generally  discarded  owing  to  the  great 
wear  on  the  pump  and  pipe  by  the  attrition  of  the  sand.  With 
a  true  slime  the  wear  is  much  less  than  if  the  charge  contains 


Fig.  10.  —  The  Trent  Agitator. 

sand.  Centrifugal  pumps  for  this  purpose  are  equipped  with 
liners  that  may  be  removed  when  worn,  but  no  liner  or  stuffing- 
box  arrangement  has  yet  been  made  that  will  last  for  any  con- 
tinued length  of  time.  Aeration  with  this  form  of  agitation  is 
provided  by  flowing  the  pulp  over  an  apron  on  introducing  it  to 
the  top  of  the  tank  and  by  means  of  an  air  valve  between  the 
tank  and  the  pump  allowing  a  small  quantity  of  air  to  be  drawn 
in  and  pumped  with  the  pulp.  A  patented  method  of  using  the 


SLIME  TREATMENT  AND  AGITATION          121 

centrifugal  pumps  for  agitating  consists  in  using  a  deep  cone- 
bottomed  tank  which  has  a  hollow,  central  column.  The  centrif- 
ugal pump  discharges  slimy  solution  upward  into  the  foot  of 
the  column,  lifting  the  pulp  up  through  the  column  by  its  force, 
as  the  hydraulic  elevator  does,  and  in  that  way  starting  and 
keeping  up  a  circulation  similar  to  that  with  the  Pachuca  tank. 
A  shield  or  cap  is  suspended  from  the  top  of  the  tank  around  the 
air  lift  to  form  a  calm  zone  of  about  6  inches  between  the  shield 
and  the  outside  of  the  tank.  The  slimy  solution  passing  through 
the  centrifugal  pump  is  drawn  from  the  top  of  this  calm  zone, 
and  is  very  dilute  and  free  from  sand,  consequently  it  does  not 
cause  excessive  wear  on  the  pump  and  piping. 

An  agitator  combining  the  principle  of  the  mechanical  stirrer 
and  the  use  of  centrifugal  pumps  is  the  Trent  agitator,  as  shown 
in  Fig.  10.  With  this  agitator  the  thinner  slime  taken  from  the 
top  of  the  charge  is  pumped  by  a  centrifugal  pump  through  the 
bottom  of  the  tank  into  a  revolving  four-armed  stirrer,  from  which 
the  slime  is  emitted  by  a  number  of  discharges  set  along  the  length 
of  each  arm,  the  discharges  being  at  right  angles  to  the  arms. 
The  force  of  the  discharge  causes  the  arms  to  revolve  in  the  same 
manner  as  a  Butters  and  Mein  sand-pulp  distributor.  The  same 
principle  can  be  employed  by  using  air  under  pressure  instead  of 
solution  to  cause  the  arms  to  revolve. 

The  Hendryx  agitator,  as  shown  in  Fig.  11,  is  one  of  the  most 
successful  in  use.  It  consists  of  a  cone-bottom  tank  of  ordinary 
height  in  which  is  mounted  a  central  column  or  tube.  In  the 
tube  is  a  shaft  driven  by  a  gear  overhead  the  tank.  Three  pro- 
peller blades  are  distributed  along  the  shaft.  The  rapid  revolution 
of  the  shaft  causes  the  blades  to  lift  or  force  the  pulp  up  the  tube 
to  flow  over  an  apron,  similar  to  an  umbrella,  to  the  edge  of  the 
tank,  from  which  it  sinks  to  the  bottom  of  the  cone  to  be  drawn 
into  the  central  tube  again.  The  tank  cannot  agitate  unless 
fairly  well  filled  with  pulp.  The  agitation  is  excellent,  the  wear 
little,  and  the  trouble  small  or  practically  none. 

The  Brown  or  Pachuca  tank,  Fig.  12,  invented  by  F.  C.  Brown 
and  first  used  in  Mexico  at  Pachuca,  the  air-lift  agitator,  is  con- 
sidered to  be  the  most  successful  agitating  tank.  It  consists  of 
a  cylindrical  tank  45  feet  high  and  15  feet  in  diameter,  though 
tanks  of  greater  height  and  relatively  less  diameter  are  in  use. 
For  the  treatment  of  slime  comparatively  shallow  tanks  will  suffice, 


122 


TEXT  BOOK  OF  CYANIDE  PRACTICE 


but  for  sand  a  greater  height  with  a  smaller  diameter  will  cause 
less  tendency  to  clog.  These  tanks  end  in  a  cone  with  60-degree 
sides;  the  steeper  the  cone  the  less  is  the  tendency  to  settle  and 
clog  or  pack.  Within  the  tank  is  a  hollow  column  15  inches  in 
diameter,  extending  from  within  18  inches  of  the  bottom  to 


Fig.  11.  —  The  Hendryx  Agitator. 

within  18  inches  of  the  top  of  the  tank.  A  IJ-inch  air  pipe  dis- 
charges upward  at  and  into  the  bottom  of  the  tube.  To  operate 
the  tank  it  is  filled  with  pulp,  and  air  under  pressure  is  turned 
into  the  bottom  of  the  column.  The  air  passing  upward  lightens 
and  lifts  the  column  of  pulp  within  the  tube,  causing  it  to  over- 
flow and  that  outside  the  tube  to  enter  the  bottom  by  its  greater 
hydrostatic  head.  This  results  in  circulating  the  pulp  up  through 


SLIME  TREATMENT  AND  AGITATION 


123 


Corapreswd  Air  Mite* 


the  central  tube  and  down  the  tank  outside  of  the  tube.  The 
action  is  that  of  the  air  lift  and  not  similar  to  the  hydraulic 
elevator.  That  is,  it  is  not  de- 
pendent upon  the  air  entering  the 
tube  with  sufficient  force  to  carry 
the  pulp  up,  but  on  the  lessening 
of  the  specific  gravity  or  density 
of  the  pulp  through  the  air  mixed 
and  entangled,  that  the  pulp  out- 
side may  rush  into  the  tube  to 
equalize  the  hydrostatic  head. 

The  Pachuca  tank  gives  a  thor- 
ough agitation  with  undoubtedly 
a  less  consumption  of  power  than 
any  other  agitator.  It  can  be 
easily  started  after  once  settled, 
possibly  excepting  when  run  on 
pure  sand,  in  which  case  the 
charge  should  not  be  allowed  to 
settle.  It  gives  a  good  aeration, 
for  only  a  gentle  current  of  air  is 
used,  which,  according  to  the 
theory  of  the  air  lift,  must  be- 
come more  or  less  entangled  with 
the  pulp.  It  will  do  excellent  work 
with  a  thick  pulp,  even  as  dense 
as  1.2  parts  of  solution  to  1  of  dry 
pulp.  It  is  not  adapted  for  de- 
cantation,  for  as  with  all  tanks  of 
relatively  great  height  and  small 
diameter,  the  settling  rate  per  ton 
of  clear  solution  obtained  is  too 
low. 

The  Just  process  has  already 
been  described  as  a  false  bottom  of 
porous,  silica-sponge  bricks  which 


Fig.  12.  —  The  Pachuca  Agitator. 


may  be  placed  in  any  flat-bottom  tank.  Air  under  pressure, 
which  may  be  as  low  as  5  pounds  and  thereby  within  the  field 
of  a  rotary  blower,  is  introduced  underneath  the  false  bottom  to 
pass  through  the  bricks  in  fine  jets  and  keep  the  pulp  in  agita- 


124  TEXT  BOOK  OF  CYANIDE  PRACTICE 

tion  and  suspension.  A  similar  method  of  agitation  by  intro- 
ducing the  air  through  perforated  pipes  was  early  tried,  but  found 
impracticable  on  account  of  the  rapid  clogging  of  the  pipes  and 
the  poor  distribution  of  the  air. 

Agitation  by  air  is  supposed  to  cause  a  greater  consumption  of 
cyanide  through  the  formation  of  hydrocyanic  acid,  though  it 
has  not  been  demonstrated  to  be  a  fact.  Air  agitation  causes  an 
increased  consumption  of  lime  by  the  CO2  of  the  air  uniting  with 
the  lime  to  form  a  carbonate.  The  calcium  carbonate  formed 
in  this  way  and  otherwise  gives  trouble  by  coating  or  clotting  the 
pores  of  the  leaf  niters  so  that  they  become  impermeable  and 
require  to  be  frequently  treated  with  dilute  hydrochloric  acid  to 
dissolve  out  the  lime. 


CHAPTER  X 
DECANTATION 

THE  decantation  system  was  the  first  method  devised  for 
treating  slime,  and  was  the  principal  one  used  until  the  invention 
and  perfection  of  the  leaf  or  vacuum  filter.  A  large  number  of 
slime  plants  were  working  until  recently  by  the  decantation  proc- 
ess and  it  now  plays  a  part  in  many  equipped  with  modern  filter- 
ing devices.  It  is  used  in  them  to  remove  part  of  the  dissolved 
metal  that  the  amount  lost  by  being  discharged  in  the  residue 
from  the  filter,  through  the  low  efficiency  of  the  filter  in  washing 
or  its  use  as  a  dewaterer  only  and  without  washing,  may  be  as 
low  as  possible.  Decantation  cannot  be  entirely  eliminated 
until  filtering  devices  do  more  efficient  work  then  they  are  doing 
under  average  conditions  to-day,  for  it  seems  to  be  a  well-accepted 
rule  that  pulp  containing  rich  solution  should  be  sent  to  the  fil- 
ters only  after  the  value  of  the  solution  has  been  reduced. 

Theory  of  the  Decantation  Process.  —  The  decantation  proc- 
ess depends  upon  the  principle  that  if  1  ton  of  dry  slime  having 
a  value  of  $5.00  per  ton  in  dissolvable  gold  and  silver  is  agitated 
with  4  tons  of  solution  until  the  maximum  dissolution  has  been 
effected,  allowed  to  settle,  and  the  clear  solution  syphoned  off 
until  the  slime  contains  one  part  of  dry  pulp  and  one  part  of  so- 
lution or  50  per  cent  moisture,  3  tons  of  solution  or  three-fourths 
of  the  dissolved  metal  will  have  been  removed,  an  extraction 
(referring  to  the  dissolved  gold  and  silver)  of  75  per  cent.  If 
3  tons  of  barren  solution  are  now  added  for  each  ton  of  the  dry 
pulp,  the  slime  agitated  for  a  thorough  mixing,  left  settle,  and 
again  decanted  down  to  50  per  cent  moisture,  there  will  be  an 
extraction  of  three-fourths  of  the  remaining  value  or  a  total 
extraction  of  93f  per  cent,  with  31  cents  of  dissolved  metal  per 
ton  of  dry  pulp  yet  remaining.  A  repetition  of  the  cycle  of 
operations  will  bring  the  total  extraction  of  the  dissolved  metal 
to  98.4  per  cent,  which  would  leave  8  cents  per  ton  in  the  residue. 
While  another  cycle  would  bring  the  extraction  or  efficiency  of 

125 


126  TEXT  BOOK  OF  CYANIDE  PRACTICE 

the  washing  up  to  99.6  per  cent  and  give  a  residue  containing  2 
cents  in  dissolved  metal. 

The  use  of  a  larger  volume  of  solution  for  each  wash  will  reduce 
the  number  of  washes  required  or  increase  the  efficiency  of  the 
washing,  likewise  when  the  slime  is  settled  to  a  smaller  percent- 
age of  moisture.  This  principle  is  illustrated  in  the  case  of  a 
dilution  of  four  parts  solution  to  one  part  of  pulp  drawn  down  to 
one  and  one,  giving  a  wash  extraction  of  75  per  cent.  Had  the 
dilution  been  eight  to  one,  the  wash  extraction  would  be  87.5 
per  cent.  While  had  the  pulp  been  drawn  down  to  two  of  solu- 
tion to  one  of  dry  pulp  (66f  per  cent  moisture),  the  wash  extrac- 
tion would  only  be  50  per  cent. 

Decantation  Process  in  Practice.  —  In  plant  practice  it  is 
impossible  to  obtain  such  satisfactory  results  in  an  economic  way 
or  to  carry  the  washings  to  the  extent  that  may  be  theorized. 
The  defects  of  the  process  are  the  inordinate  amount  of  the  fol- 
lowing: the  solution  to  be  handled  and  precipitated,  the  con- 
sumption of  lime  for  settling  purposes,  the  labor  in  giving  the 
washes,  the  time  consumed  in  mixing  solution  and  pulp  and 
resettling,  the  pulp  and  solution  tankage  space,  and  the  water, 
chemicals,  and  dissolved  metal  discharged  with  the  residue. 
Also  the  inability  in  many  cases  to  get  a  thorough  intermixing 
of  the  settled  slime  and  the  wash  solution. 

When  treating  100  tons  of  dry  pulp  per  24  hours  with  a  dilu- 
tion of  four  of  solution  to  one  of  dry  pulp,  it  may  require  four 
days  to  give  the  necessary  treatment  of  dissolving  and  taking  off 
three  solutions.  This  may  be  presumed  to  be  equal  to  400  tons 
of  dry  slime  in  the  plant  in  the  process  of  being  treated,  requiring 
2000  tons  of  diluted-pulp  tankage  space,  and  the  handling  of  900 
tons  of  decanted  solution  per  day.  If  the  mill  crushes  in  water 
it  will  be  almost  impossible  to  wash  the  slime  with  any  water,  or 
the  bulk  of  the  solution  in  the  plant  will  increase  to  a  point  where 
it  must  be  run  to  waste.  Consequently,  a  pulp  discharged  con- 
taining 50  per  cent  of  moisture  will  cause  a  loss  of  1  ton  of  the 
final  wash  solution  for  each  ton  of  the  dry  slime  discharged. 
The  cyanide  in  this  last  wash,  often  a  half  pound  or  more  per 
ton  of  solution,  which  is  discharged  will  be  lost.  If  the  crushing 
is  done  in  solution  the  theoretical  amount  of  water  that  may  be 
used  in  washing  is  equal  to  that  discharged  with  the  residue. 
Consequently  100  tons  of  water  may  be  mixed  with  the  100  tons 


DECANTATION  127 

of  dry  pulp  and  the  same  amount  of  solution  (to  which  proportion 
the  pulp  has  settled),  and  allowed  to  settle,  after  which  it  should 
be  possible  to  syphon  off  100  tons  of  clear  solution.  In  this  way 
the  cyanide  mechanically  lost  per  ton  of  dry  slime  is  equal  to 
one-half  the  number  of  pounds  in  a  ton  of  the  last  cyanide  solu- 
tion added. 

Decantation  practice  does  not  proceed  along  strictly  theo- 
retical lines,  but  according  to  methods  which  may  be  deemed 
most  expedient,  one  of  the  principal  features  of  which  is  that  not 
all  of  the  solution  is  precipitated.  That  which  comes  off  in  a 
final  or  the  final  decantations,  with  only  a  small  amount  of  value, 
is  used  as  a  first  or  the  first  washes  to  dilute  and  remove  the  rich 
solution  from  a  new  charge,  then  precipitated  to  be  again  used 
as  a  final  wash,  it  being  considered  more  profitable  to  proceed 
this  way  than  to  precipitate  all  the  solution.  The  time  required 
for  agitating  and  settling  depends  upon  the  nature  of  the  ore  and 
must  necessarily  vary  in  each  case.  The  following  is  an  example 
of  decantation  practice  with  an  ore  crushed  in  water,  settling  one 
to  one,  treated  with  a  dilution  of  4  tons  of  solution  to  1  of  dry 
pulp,  and  given  three  washes.  The  pulp  is  drawn  from  the  set- 
tling or  stock  tanks  to  the  agitator;  to  each  ton  of  the  dry  pulp 
is  added  3  tons  of  the  unprecipitated  intermediate  or  second 
wash  from  a  previous  charge.  Cyanide  is  added  to  bring  the 
strength  up  to  .05  per  cent  (1  pound)  KCN,  no  lime  being  nec- 
essary on  account  of  the  high  protective  alkalinity  of  the  solu- 
tion. Agitation  is  carried  on  for  12  hours,  by  which  time  the 
maximum  dissolution  has  been  effected.  A  short  time  before 
stopping  the  agitation  2  pounds  of  lime  per  ton  of  ore  are  added 
to  be  thoroughly  mixed  for  settling  the  charge.  After  the  agita- 
tion has  been  stopped,  the  solution  is  drawn  off  as  fast  as  it  be- 
comes clarified  by  the  settling  of  the  slime,  through  a  hinged 
pipe  left  down  on  the  inside  of  the  tank.  The  solution  often 
contains  some  suspended  matter  or,  from  carelessness  in  decanta- 
tion, contains  considerable  slime,  and  is  run  through  a  sand  filter 
to  be  clarified  before  being  precipitated.  Eighteen  hours  are 
required  for  settling  and  decanting  the  first  wash.  Gold  and 
silver  to  the  amount  of  $5.00  per  ton  have  been  dissolved  from  the 
ore;  this  has  been  diluted  by  the  four  parts  of  solution  to  enrich 
each  ton  of  solution  $1.25,  to  which  is  added  $0.45,  for  the  un- 
precipitated intermediate  wash  carried  $0.60  per  ton  and  3  tons 


128  TEXT  BOOK  OF  CYANIDE  PRACTICE 

of  this  solution  were  used  to  1  of  water  in  the  settled  slime.  This 
gives  a  solution  of  $1.70  to  be  decanted  and  sent  to  the  zinc 
boxes  as  the  first  wash.  After  the  decantation  there  still  remains 
1  ton  of  solution  worth  $1.70  with  each  ton  of  dry  slime.  To 
each  ton  of  this  solution  is  added  3  tons  of  the  unprecipitated 
final  or  third  wash  of  a  previous  charge,  containing  $0.16  per  ton. 
This  gives  a  value  to  the  resulting  mixture  of  (1.70  -f-  4)  +  (f  of 
0.16)  =  $0.55  per  ton  of  solution.  An  agitation  of  3  hours  is 
given  to  thoroughly  mix  the  charge,  followed  by  settling  and 
decanting  for  18  hours  to  remove  the  second  or  intermediate 
wash.  After  which  3  tons  of  a  precipitated  first  wash  solution 
practically  barren  are  added  and  agitated  for  1J  hours  and  the 
charge  pumped  into  another  tank  to  insure  thorough  mixing, 
requiring  2  hours.  Another  settling  and  decanting  period  of 
18  hours  is  given  to  draw  the  solution  down  to  a  one  and  one 
consistence.  TJie_value  _of..iMs last  wash  is  a  little  higher  than 
the  theoretical  amount  which  should  be  ($0.55  -f-  4)  =  $0.14 
per  ton,  consequently  the  residue  which  is  now  discharged  con- 
tains a  little  over  $0.14  in  dissolved  metal  per  ton  of  dry  pulp, 
and  an  amount  in  cyanide  equal  to  that  of  the  last  wash  given, 
which  was  about  0.4  pound  KCN.  Had  all  the  wash  solution 
been  precipitated,  the  final  tailing  would  have  a  theoretical  value 
of  8  cents  in  dissolved  metals.  If  the  intermediate  wash  had 
been  precipitated,  but  not  the  final,  the  theoretical  value  remain- 
ing would  be  9  cents.  In  the  first  case  6  tons  more  of  solution 
would  have  to  be  precipitated  for  each  ton  of  dry  pulp  at  a  cost 
of  3  cents  per  ton  of  solution  or  18  cents  per  ton  of  ore.  In  the 
second  case,  3  tons  more  of  solution  would  have  to  be  precipi- 
tated at  a  cost  of  9  cents  per  ton  of  ore  to  obtain  the  theoretical 
difference  of  5  cents  (.14  —  .09). 

If  the  dissolution  of  the  last  of  the  gold  and  silver  is  slow,  the 
agitation  may  be  stopped  and  the  first  wash  removed  with  a 
reliance  on  the  solvent  activity  of  fresh  solution  or  of  the  long, 
general  contact  to  effect  the  dissolution  still  to  be  made  in  time 
to  allow  it  to  be  removed  by  the  washes.  Owing  to  the  inability 
to  get  a  thorough  intermixing  with  mechanical  agitators  and 
flat-bottomed  tanks,  it  is  the  custom  in  many  plants  to  transfer 
the  pulp  from  one  tank  to  another  when  applying  a  wash.  In 
this  way  any  sand  that  has  hugged  the  bottom  and  corners  of 
the  tank  together  with  its  adsorbed  rich  moisture  responds  to 


DECANTATION  129 

the  washing  process.  If  only  one  transfer  can  be  made,  it  should 
be  effected  after  the  bulk  of  the  value  has  been  removed  by  one 
or  two  first  decantations.  The  pulp  may  be  transferred  after 
the  last  agitation  to  a  deeper  settling  tank  than  usual  and  with- 
out an  agitating  device,  wherein  only  the  thicker,  denser  pulp  is 
drawn  off  intermittently  from  the  bottom  of  the  tank  as  a  residue 
to  go  to  the  slum  pond.  The  drawing  off  of  part  of  the  settled 
pulp  together  with  a  decantation  of  the  clear  solution  from  the 
top  makes  room  for  each  charge  as  added;  the  entire  amount 
of  pulp  not  being  withdrawn  at  any  time.  The  use  of  compara- 
tively deep  tanks,  preferably  with  cone  bottoms,  in  this  way,  as 
a  more  or  less  continuous  or  intermittent  method  of  decanting 
and  discharging,  gives  a  sludge  to  be  discharged  having  a  higher 
percentage  of  dry  slime,  owing  to  the  greater  length  of  time 
allowed  for  settling  and  the  pressure  weight  of  the  deep  column 
of  pulp.  Many  attempts  have  been  made  to  make  use  of  these 
principles  in  connection  with  that  of  cone  or  other  overflow 
settling  devices,  especially  for  a  continuous  washing  and  treat- 
ment system,  but  without  much  practical  success  except  in  the 
case  of  the  last  wash. 

Mechanical  Decantation  Processes.  —  The  Adair-Usher  proc- 
ess developed  in  South  Africa  is  dependent  somewhat  on  the 
above  principles.  After  the  metal  has  been  dissolved,  and  with- 
out allowing  more  than  a  slight  settling  of  the  slime,  barren 
solution  is  introduced  through  pipes  evenly  over  the  bottom  of 
the  slime  tank,  which  should  be  comparatively  deep.  This  solu- 
tion enters  in  sufficient  quantity  to  rise  at  a  rate  slightly  slower 
or  equal  to  the  settling  rate  of  the  slime  and  to  always  give  a 
clear  overflow  of  solution  from  the  tank.  In  theory  the  barren 
solution  lifts  or  displaces  the  rich  solution  and  washes  the  slime 
in  suspension.  When  the  washing  has  been  carried  as  far  as 
practicable,  the  inflow  of  solution  is  stopped,  the  slime  left  settle, 
and  the  clear  solution  decanted  off  as  usual.  This  process  does 
not  do  away  with  decantation  in  its  entirety,  but  is  only  an 
adjunct  or  expedient  to  reduce  the  number  of  decantations. 

While  continuous  decantation  without  mechanical  means  has 
not  been  a  practical  success,  continuous  decantation  with  mechani- 
cal appliances  has  been  rendered  possible  by  the  introduction  of 
the  Dorr  pulp  thickener.  This  appliance  is  now  in  use  dewatering 
the  pulp  to  a  low  percentage  of  moisture,  followed  by  diluting  the 


130  TEXT  BOOK  OF  CYANIDE  PRACTICE 

pulp  with  wash  solution  to  be  again  dewatered,  using  a  sufficient 
number  of  such  machines  to  thoroughly  wash  out  the  dissolved 
metal.  This  method  seems  to  be  well  adapted  for  some  conditions 
or  in  a  modified  form  to  precede  filtration  for  the  purpose  of  re- 
ducing the  value  of  the  pulp  and  solution  supplied  to  the  filter, 
thereby  lessening  the  mechanical  loss  through  the  low  efficiency 
of  the  filter  wash. 


CHAPTER  XI 
FILTRATION 

Plate  and  Frame  Filter  Press.  —  Owing  to  the  trouble  and  low 
efficiency  encountered  in  treating  slime  by  the  decantation  process, 
the  plate  arid  frame  filter  press  was  early  made  use  of  for  dewatering 
and  washing  the  dissolved  gold  and  silver  out  of  slime  pulp.  The 
filter  press  shown  in  Fig.  13  was  already  in  wide  use  in  clay- 
working  plants  for  dewatering  a  thin,  clay  pulp,  and  in  the  sugar- 
making  industry  for  filtering  the  juices  and  washing  the  residuum 
in  the  process  of  making  sugar.  The  plate  and  frame  filter  press 
as  used  in  the  cyanide  process  consists  of  a  number  of  solid  metal 
plates  with  a  hollow  plate  or  frame  alternated  between  each. 
These  plates  are  square  or  rectangular  in  shape  and  up  to  3  or  4 
feet  in  dimensions,  the  frames  being  from  2  to  4  inches  thick. 
The  alternate  plates  and  hollow  frames  are  set  in  an  upright 
position  face  to  face  by  means  of  projecting  arms  or  shoulders 
on  each  plate  and  frame  resting  on  two  strong  bars  on  each  side 
of  the  assembled  press.  This  makes  a  box-like  structure  with  a 
height  and  width  equal  to  the  dimensions  of  the  plates  and  frames, 
and  with  a  length  dependent  upon  their  thickness  and  their 
number,  which  may  be  as  high  as  fifty.  Each  end  of  the  press 
is  closed  with  a  solid  plate,  while  between  each  plate  and  frame  is 
placed  a  sheet  of  canvas  as  a  filter  cloth.  At  the  ends  of  the 
press  are  screw  devices  for  forcing  the  plates  together  and  thereby 
making  the  press  water-tight,  or  hydraulic  or  air  pressure  instead 
of  hand  screws  is  used  to  open  and  close  the  presses.  Each 
plate  and  frame  contains  lugs  or  shoulders  bored  with  holes. 
When  the  press  is  in  position  these  holes  form  a  passageway  for 
the  slime  pulp  and  solution.  The  passageway  for  the  slime  pulp 
is  provided  with  a  small  opening  into  each  frame  or  hollow  plate 
only.  This  allows  the  pulp  under  pressure  to  enter  and  fill 
each  hollow  frame.  The  solution  in  the  pulp  under  pressure  is 
forced  through  the  canvas  on  one  of  the  sides  and  runs  down 
between  the  canvas  and  the  solid  plate,  which  is  corrugated  to 

131 


132 


TEXT  BOOK  OF  CYANIDE  PRACTICE 


better  allow  the  passage  of  the  solution  between  the  canvas  and 

the  plate,  to  a  small  open- 
ing in  the  corner  of  the 
plate  where  it  runs  to  an- 
other passageway  or  chan- 
nel of  bored  holes  leading 
to  the  solution  tank.  In 
some  types  each  plate  is 
provided  with  small  indi- 
vidual cocks  emptying  into 
a  launder  leading  to  the 
solution  tank.  The  flow  of 
pulp  is  stopped  as  soon  as 
the  press  is  filled  with  a 
solid  cake  of  pulp,  and  wash 
solution  or  air  followed  by 
wash  solution  is  pumped 
through  a  third  passage- 
way to  enter  between  the 
other  canvas  and  the  other 
corrugated  side  of  each 
plate.  Whence  it  is  forced 
through  the  canvas  into  the 
cake  of  pulp,  washing  it  or 
displacing  the  moisture  in 
it,  passing  through  the  op- 
posite filter  cloth,  and  run- 
ning down  between  the 
corrugations  to  pass  out 
through  the  hole  in  the 
corner  of  the  .  plate  into 
the  passageway  leading  to 
the  solution  tank,  just  as 
the  solution  does  which  is 
expressed  from  the  pulp  in , 
filling  the  press.  After  suf- 
ficient washing  with  barren 
solution,  a  water  wash,  per- 
haps preceded  by  an  air  wash  or  displacement,  is  introduced 
through  the  same  passageway.  Finally  air  under  pressure  is  ad- 


FILTRATION 


133 


mitted,  which  displaces  a  large  part  of  the  moisturise  that  a  cake 
containing  as  low  as  15  to  25  per  cent  of  moisture  may  be  obtained. 
After  which  the  closing  screws  of  the  press  are  opened,  allowing 
the  plates  and  frames  to  be  separated  and  the  washed  cake  of 
slime  to  be  dropped  into  a  car  or  sluice  for  discharge  to  the  resi- 
due dump.  The  plates,  frames,  and  filter  cloths  are  next  brought 


Fig.  14.  —  Plate  and  Frame  of  Filter  Press. 

A,  Passageway  for  pulp.     B.  Passageway  for  entering  solution.     C.  Passageway  for 
departing  solution. 

together,  the  closing  screws  are  tightened,  and  a  new  cycle  of 
operations  is  started. 

The  pulp  may  be  forced  into  the  press  by  pumps  capable  of 
giving  a  high  pressure,  by  gravity  under  a  high  head,  or  by  com- 
pressed air  and  a  monteju,  though  the  last  method  is  practically 
obsolete.  The  monteju  is  a  large,  closed,  metal  tank  or  receiver 
into  which  the  pulp  is  run  as  required.  To  fill  the  press,  the 
monteju  is  closed  and  air  under  pressure  admitted  at  the  top  to 
force  or  displace  the  pulp  into  the  press.  The  principal  advan- 
tage of  the  monteju  is  the  lack  of  'wear  through  the  attrition  of 
the  pulp. 

Filter  Press  Practice  in  Australia.  —  The  following  details*  of 
treatment  with  the  Dehne  press,  the  bes^  known  of  the  standard 
filter  presses  and  which  has  been  successfully  used  in  Australia, 
represents  the  highest  type  of  work.  The  slime  from  the  agita- 
tors having  a  consistence  of  about  1  and  1,  is  pumped  to  the 
presses  by  a  Pern  pump  having  three  plungers,  12  by  10  inches, 
running  at  20  revolutions  per  minute.  This  is  a  powerful  pump 

*  M.  W.  von  Bernewitz  in  "  Slime  Treatment  at  Kalgoorlie,"  Min.  and 
Sci.  Press,  Dec.  14,  1907.  More  Recent  Cyanide  Practice,  pp.  82. 


134  TEXT  BOOK  OF  CYANIDE  PRACTICE 

and  will  fill  a  press  in  10  minutes,  lifting  in  that  time  about  10 
tons  of  pulp,  and  charging  against  a  final  pressure  of  60  pounds 
per  square  inch.  The  time  taken  in  filling  may  be  divided  as 
follows : 

Up  to  25-lb.  pressure 4  min. 

Up  to  50-lb.  pressure 3  min. 

Up  to  60-lb.  pressure 1  min. 

Finishing  with  safety  valve  blowing  off  at  60-lb 2  min. 

Total 10  min. 

Average  screen  tests  of  the  ore  are: 

Held  on  40-mesh Nil  per  cent 

Held  on  60-mesh 0.5  per  cent 

Held  on  80-mesh 2.5  per  cent 

Held  on  100-mesh 4.3  per  cent 

Held  on  150-mesh 4.9  per  cent 

Passed  150-mesh 87.5  per  cent 

The  three  Dehne  presses  each  have  50  3-inch  frames  for  the 
slime.  Each  press  will  hold  about  4.5  tons  dry  slime.  After  a 
press  is  filled,  the  slime  is  washed  for  25  minutes  with  weak 
cyanide  solution,  and  a  water  wash  of  5  minutes  at  100-pound 
pressure,  during  which  time  each  ton  of  slime  is  washed  with  2 
tons  of  solution.  The  washing  is  done  by  a  similar  pump  to  that 
used  in  filling,  only  that  it  runs  at  13  revolutions  per  minute. 
The  final  water  wash  is  dispensed  with  when  there  is  an  excess  of 
mill  solution,  the  press  getting  30  minutes  with  wash  solution. 
The  decrease  in  the  assay  value  of  the  solution  during  the  wash- 
ing is: 

At  start  of  wash $12.50 

After  5  min 6.60 

After  10  min 1.50 

After  15  min • 1.50 

After  20  min 1.00 

After  25  min 1.00 

After  30  min .  0.80 

After  washing,  the  content  of  the  press  is  dried  with  air  for  10 
minutes  at  80-pound  pressure.  The  press  is  then  opened  ready 
for  discharging.  Two  men  empty  11  presses  per  shift  of  8  hours, 
say  50  tons,  onto  a  traveling  horizontal  belt-conveyor  18  inches 
wide.  Most  of  the  solution  used  in  washing  the  presses  passes 


FILTRATION  135 

into  the  mill  solution  to  be  again  used  in  the  grinding  pans,  etc. 
The  cyanide  solution  is  made  up  to  .07  per  cent  (1.4  pounds) 
and  the  consumption  averages  1  pound  per  ton  treated.  An 
average  of  three  months'  costs  of  slime  treatment  is: 

Agitation  and  cyaniding $0.34  per  ton 

Filter-pressing 0.41  per  ton 

Precipitation,  etc 0.12  per  ton 

Disposal  of  residue 0.04  per  ton 

Total 0.91  per  ton 

The  time  taken  in  the  different  press  operations  is : 

Filling  press 10  min. 

Washing 30  min. 

Drying 10  min. 

Discharging 30  min. 

Screwing-up,  etc ' 10  min. 

Total li  hours 

The  daily  capacity  is  123  tons  of  roasted  telluride  ore  and  43 
tons  of  retreated  old  residue,  having  an  average  recovered  value 
of  $14.10. 

The  Merrill  Press.  —  The  Merrill  press,  as  developed  by  C.  W. 
Merrill  and  shown  in  Fig.  15,  does  not  differ  in  principle  from  the 
standard  filter  press.  Its  dimensions  are: 

Number  of  frames 64  to  92. 

Size  of  frames 4  by  6  ft. 

Length Up  to  45  ft. 

Capacity  per  charge Up  to  25  tons. 

Thickness  of  cake 3  to  4  ins. 

With  ores  in  which  the  metal  goes  into  solution  quickly  and 
that  are  not  too  slimy,  the  dissolution  as  well  as  the  washing  may 
take  place  in  the  press.  The  pulp  is  dewatered  down  to  3  parts 
of  water  to  1  of  dry  slime,  or  thicker  if  there  is  a  tendency  for 
the  sand  to  classify  in  the  filling  process.  It  is  run  into  the  press 
by  gravity  under  a  pressure  of  20  to  30  pounds  per  square  inch 
(equal  to  40  to  70  feet  fall).  After  the  press  is  filled,  the  water 
is  displaced  and  the  pulp  partly  dried  by  air  under  pressure, 
when  cyanide  solution  is  slowly  pumped  through  the  charge  fol- 
lowed by  air  under  pressure.  The  application  of  the  dissolving 


136  TEXT  BOOK  OF  CYANIDE  PRACTICE 

solution  and  the  aeration  is  alternated  until  the  precious  metals 
are  dissolved,  when  the  usual  washing  with  weak  solution  and 
water  with  final  air  displacement  follows.  On  the  completion  of 
the  treatment,  which  may  require  6  hours,  the  charge  is  washed 
from  the  press  by  water  introduced  through  a  "  sluicing  bar," 
which  is  a  pipe  extending  lengthwise  throughout  the  press.  This 
pipe  is  provided  with  nozzles  in  each  chamber  and  an  outside 
mechanism  which  causes  it  to  revolve  back  and  forth  sufficiently 
to  direct  the  water  discharged  from  the  nozzles  into  every  part 
of  each  frame  or  chamber.  In  this  way  the  charge  is  washed  out 


Fig.  15.  —  The  Merrill  Filter  Press. 

of  the  press  through  the  balance  of  the  passageway  in  which  the 
"  sluicing  bar  "  lies.  From  4  to  8  tons  of  water  per  ton  of  dry 
slime  are  required  to  wash  the  press  out.  A  large  part  of  the 
water  may  be  saved  by  the  use  of  pulp-thickening  tanks.  Where 
the  metal  has  been  dissolved  before  entering  the  press,  the 
operations  are  similar  to  those  of  an  ordinary  filter  press,  except 
in  regard  to  sluicing  out  the  press. 

It  is  reported  that  50,000  tons  of  dry  slime  have  been  treated 
per  month  at  the  Homestake  slime  plant  at  a  total  cost  of  25 
cents  per  ton,  of  which  the  filtering  cost  amounted  to  If  cents 
per  ton.  The  value  of  the  untreated  slime  is  said  to  be  about 
85  cents  per  ton  and  the  extraction  to  be  90  per  cent.  This  is 
a  record  that  has  never  been  approached  by  any  other  slime 
treatment  or  filtration  system,  but  much  of  which  must  be 
credited  to  the  costly  plant  and  large  tonnage  available. 


FILTRATION  137 

The  plate  and  frame  filter  press  is  best  adapted  for  the  granu- 
lar slime  of  quartzose  ore,  and  then  requires  the  addition  of  con- 
siderable fine  sand  to  render  the  slime  more  permeable  by  the 
solution.  The  filter  press  as  ordinarily  used  will  not  do  good 
washing  on  an  abnormally  talcose,  clayey  slime.  Such  material 
is  washed  in  the  Merrill  press  (dissolution  of  the  value  having 
taken  place  before  filling  the  press)  by  what  is  termed  "  center- 
washing."  In  this  method  the  solution  expressed  from  the  pulp 
is  allowed  to  flow  through  both  canvases  and  tEe  frames  are  not 
filled  with  solid  cakes  of  pulp.  An  opening  of  a  quarter  of  an 
inch  or  more  is  allowed  in  the  center  of  each  cake,  through  which 
the  barren  solution  immediately  following  the  pulp,  without  any 
interlude  of  aeration,  and  finally  the  water  wash  and  air  displace- 
ment pass  to  wash  the  metal-bearing  solution  out  of  the  slime. 
The  following  is  the  data  on  a  cycle  of  operations  working  in 
this  way:  Filling  with  a  pulp  of  Ij  parts  of  solution  to  1  of  slime, 
30  minutes;  washing  with  2J  tons  wash  solution  and  water  per 
ton  dry  slime,  35  minutes;  discharging,  45  minutes;  total,  1 
hour  and  50  minutes.  , 

Vacuum  or  Pressure  Leaf  Filters.  —  The  vacuum  or  pressure- 
leaf  filter  differs  entirely  from  the  plate  and  frame  filter  press. 
The  principle  of  these  filters  is  the  use  of  a  flat  slip  or  bag  of  can- 
vas over  a  suitable  thin  frame  of  wood  or  metal.  The  inside  of 
the  filtering  leaf  in  the  suction  type  is  connected  to  a  suction  or 
vacuum  pump.  On  completely  immersing  the  leaf  into  a  homoge- 
neous slime  pulp  and  starting  the  suction  removing  the  air  and 
solution  from  the  interior  of  the  leaf,  the  atmospheric  pressure 
causes  the  slime  to  collect  on  the  leaf  and  the  solution  to  pass 
within  and  be  drawn  through  the  pump  or  into  the  vacuum  tank 
through  which  the  pump  works.  This  results  in  collecting  a 
layer  of  thickened  pulp  on  the  filter  leaf,  which  increases  in 
thickness  until  the  atmospheric  pressure  is  no  longer  able  to 
force  the  solution  through  the  cake  formed  and  consequently 
there  is  a  vacuum  within  the  leaf.  The  success  of  the  leaf  filter 
has  hinged  upon  the  equal  permeability  of  the  cake  formed,  for 
should  any  part  at  the  time  of  forming  the  cake  be  more  per- 
meable than  the  rest,  more  pulp  will  be  drawn  to  that  part  and 
more  solution  will  pass  through  it,  until  the  resistance  to  filtra- 
tion at  this  point  and  all  others  is  equal.  With  a  pulp  that  is 
homogeneous  and  a  filter  cloth  of  equal  permeability,  a  cake  of 


138 


TEXT  BOOK  OF  CYANIDE  PRACTICE 


FILTRATION  139 

even  thickness  will  be  formed.  But  should  the  pulp  tend  to 
classify  and  the  sand  or  pulp  in  general  sink  to  the  bottom,  the 
lower  part  of  the  cake  will  be  thick  and  sandy,  while  the  upper 
will  be  thin  and  slimy.  Similarly,  a  spot  on  the  canvas  leaf 
that  is  less  porous,  through  a  coating  of  carbonate  of  lime  or  other, 
will  have  a  thinner  coating  of  material,  but  one  of  the  same  com- 
position as  that  of  the  surrounding  cake. 

Having  formed  a  cake  upon  the  leaf  as  thick  as  the  atmospheric 
pressure  will  allow,  it  may  be  removed  from  the  pulp  without 


Fig.  17.  —  The  Butters  Filter. 

breaking  or  cracking  and  immersed  in  a  wash  solution,  provided 
the  vacuum  is  continued  to  an  extent  just  sufficient  to  hold  the 
cake  on  the  leaf  intact.  The  continuation  of  the  vacuum  will 
cause  the  atmospheric  pressure  to  force  the  solution  through 
the  cake  into  the  interior  of  the  leaf  to  be  withdrawn  by  the 
vacuum  pump.  This  passage  of  the  solution  through  the  charge 
or  cake  is  the  washing  process,  just  as  takes  place  in  a  leaching 
vat  or  in  the  plate  and  frame  filter  press.  An  equal  amount  of 
solution  will  be  drawn  through  all  parts  of  the  leaf,  even  if  the 
texture  and  thickness  of  the  cake  vary  as  noted  before,  for 
unless  the  cake  cracked  or  sloughed  during  the  removing  process, 
its  resistance  will  be  the  same  all  over  its  area. 


140  TEXT  BOOK  OF  CYANIDE  PRACTICE 

After  passing  barren  solution  or  wash  water  through  the  cake 
until  the  dissolved  metal  is  displaced  and  removed  from  the 
interior  of  the  leaf,  the  leaf  and  its  cake  are  removed  and  exposed 
in  the  air.  The  vacuum  is  continued  to  remove  as  much  of  the 
wash  water  as  practicable,  especially  should  the  cake  be  washed 
in  barren  solution  and  it  be  desired  to  keep  the  mechanical  loss 
of  cyanide  as  low  as  possible.  The  next  step  is  to  introduce  air 
and  water  into  the  interior  of  the  leaf  to  remove  or  slough  off  the 
treated  slime,  when  a  new  cycle  of  operations  may  be  taken  up. 

Classification  of  Leaf  Filters.  —  The  different  leaf  niters 
divide  themselves  into  two  classes,  the  suction  or  vacuum  and 
the  pressure  niters.  These  are  further  divided  into  the  station- 
ary and  movable  niters,  into  the  continuous  and  intermittent, 
and  then  into  lesser  gradations.  The  Butters  is  the  best  known 
of  the  stationary,  intermittent,  vacuum  niters.  A  large  number 
of  leaves  up  to  two  hundred  are  arranged  in  a  box  with  cone 
bottoms.  The  pulp  is  run  by  gravity  or  pumped  into  the  bottom 
of  this  box  to  rise  and  keep  the  leaves  submerged.  A  vacuum 
is  applied  to  the  interior  of  the  leaves  to  form  a  cake  an  inch  or 
more  in  thickness.  After  the  cake  is  formed,  the  surplus  pulp 
is  removed  by  gravity  or  pumping  to  the  stock  tank  supplying 
the  filter,  and  wash  solution  or  water  introduced  into  the  box 
and  drawn  through  the  cakes.  Having  removed  the  wash  solu- 
tion, the  box  may  be  filled  with  water  to  assist  in  carrying  out 
and  removing  the  slime,  or  the  slime  may  be  dropped  into  the 
bottom  of  the  box  to  receive  a  little  sluicing  or  water  to  make 
it  slide  out  and  run  to  the  slum  pond.  In  either  case  the  cake 
is  dropped  by  reversing  the  force  that  has  formed  and  held  it  in 
place,  by  turning  air  or  water  or  both  into  the  interior  of  the  leaf. 

The  Moore  is  the  best  known  of  the  movable,  intermittent 
vacuum  filters.  The  series  or  "  basket  "  of  leaves  is  fastened 
together  in  such  a  way  that  it  may  be  easily  and  quickly  lifted 
and  transferred  from  one  tank  to  another  by  means  of  a  traveling 
crane  or  a  lifting  and  revolving  device.  The  basket  of  leaves  is 
lowered  into  and  kept  submerged  in  the  stock-pulp  tank  until 
the  cake  is  formed.  It  is  then  raised  and  transferred  by  means 
of  the  crane  to  an  adjoining  wash-solution  tank  where  it  is  washed. 
After  which  it  is  lifted  and  transferred  to  a  tank  or  hopper  into 
which  the  cake  or  charge  is  dropped  in  a  way  similar  to  with  the 
Butters  filter. 


s 


141 


FILTRATION  143 

The  Oliver  shown  in  Fig.  20  is  a  vertically-revolving,  continu- 
ous vacuum  filter.  It  consists  of  a  revolving  drum  which  may  be 
as  large  as  12  feet  in  diameter  and  18  feet  broad.  The  surface  or 
face  of  the  drum  or  wheel  is  prepared  as  a  leaf-filtering  surface 


Fig.  20.  —  The  Oliver  Continuous  Filter. 

and  divided  into  a  number  of  compartments,  connected  on  the 
inside  with  a  vacuum  or  suction  pipe  and  a  pipe  for  admitting 
compressed  air.  The  drum  is  partly  immersed  in  a  tank  or  box 
of  thick  pulp  and  revolves  at  a  slow  rate  of  speed.  The  mech- 


144  TEXT  BOOK  OF  CYANIDE  PRACTICE 


Fig.  21.  —  The  Oliver  Continuous  Filter  (End  View). 
List  of  Parts. 


Filter  Drum. 
Steel  Filter  Tank. 
Cast  Iron  Pedestals. 
Steel  I  Beam  Frame. 
Manhole. 

6.  Cast  Iron  Spider  Rim. 

7.  Channel  Steel  Arms. 
Hollow  Trunnion. 
Steel  Shaft. 

Main  Bearings. 


8. 

9. 

10. 


11.  Stuffing  Boxes. 

12.  Worm  Drive  Gear. 

13.  Worm  Shaft. 

14.  Oil  Well  for  Worm. 

15.  Filter  Drive  Pulleys. 

16.  Pulleys  for  Agitator  and  Wiring. 

17.  Chain  Drive  for  Agitator. 

18.  Bevel  Gears  on  Agitator  Shafts. 

19.  Agitator  Shafts. 


FILTRATION 


145 


Fig.  22.  —  The  Oliver  Continuous  Filter  (Side  View). 
List  of  Parts. 


20.  Agitator  Shaft  Bearings. 

21.  Wood  Staves  for  Drum. 

22.  Section  Division  Strips. 

23.  Filter  Medium. 
Wire  Winding. 
Steel  Scraper. 
Scraper  Adjustment. 
Tailing  Apron. 
Vacuum  Pipes. 
Compressed  Air  Pipes. 


24. 
25. 
26. 
27. 

28. 
29. 


30.  Regrinding  Valve  Seat. 

31.  Automatic  Valve. 

32.  Adjusting  Lever  for  Valve. 

33.  Vacuum  Hose  Connection. 

34.  Compressed  Air  Connection. 

35.  Discharge  Spray  Pipe. 

36.  Emergency  Agitator  Pipe. 

37.  Drain  Flange. 

38.  Wash  WTater  Pipes. 


146 


TEXT  BOOK  OF  CYANIDE  PRACTICE 


anism  acts  automatically  to  cause  a  vacuum  which  makes  a  cake 
of  |  to  J-inch  thickness  as  the  drum  passes  through  the  pulp. 
As  the  cake  emerges  from  the  pulp  the  atmospheric  pressure 
displaces  a  large  part  of  the  solution  adsorbed  by  the  slime,  after 
which  a  line  of  wash  water  or  solution  across  the  width  of  the 
drum  applies  the  wash.  Air  is  finally  drawn  through  to  displace 


Fig.  23.  —  A  50-ton  Oliver  Continuous  Filter,  at  North  Star  Mines  Co.,  Grass 

Valley,  California. 

as  much  of  this  wash  as  possible.  Just  before  each  section  of  the 
drum  with  its  washed  and  air-dried  part  of  the  cake  reenters  the 
pulp,  the  vacuum  is  automatically  shut  off  and  air  under  a  light 
pressure  introduced  to  cause  the  cake  to  drop  off,  assisted  by  a 
scraper. 

The  Hunt  is  a  horizontally-revolving,  continuous  vacuum  filter 
as  shown  in  Fig.  24.  It  consists  of  a  horizontal,  annular  filter  bed 
underneath  which  a  vacuum  only  is  applied.  A  carriage  mounted 
inside  of  the  filter  ring  and  supported  on  a  track  outside  of  it  re- 


FILTRATION 


147 


volves  continuously.     The  pulp  is  roughly  classified  into  sand  and 
slime  and  each  is  delivered  to  a  hopper  at  the  middle  of  the  filter. 


Fig.  24.  —  The  Hunt  Continuous  Filter. 


Fig.  25.  —  Carriage  of  the  Hunt  Continuous  Filter. 

From  the  hoppers  the  pulp  runs  out  through  arms  to  be  delivered 
evenly  across  the  width  of  ,the  filter  ring.     The  sand  is  first 


148  TEXT  BOOK  OF  CYANIDE  PRACTICE 

deposited  to  form  a  good  filtering  medium,  and  is  immediately 
followed  by  a  layer  of  slime  delivered  over  it.  The  vacuum 
operates  to  withdraw  part  of  the  moisture  from  the  bed  of 
deposited  pulp,  while  a  pipe  delivering  a  spray  of  wash  solu- 
tion or  wash  water  follows  at  a  suitable  interval;  the  vacuum 
finally  drying  the  pulp  which  is  scraped  off  to  fall  over  the 
outer  edge  of  the  filter  ring  by  a  scraper  placed  in  front  of  the 
arm  delivering  the  sand.  A  novel  feature  is  the  use  of  a  filter 
bed  consisting  of  triangular,  wooden  slats  filled  with  coarse  sand 
and  dispensing  with  filter  cloths.  A  similar  device  is  being 
used  in  South  Africa  to  dewater  the  sand  before  adding  cyanide 
solution  and  transferring  to  the  leaching  tanks. 

The  Ridgeway  Filter,  as  shown  in  Fig.  26,  is  a  horizontally-re- 
volving, continuous  vacuum  filter  with  an  intermittent  action.  It 
consists  of  an  annular  ring  made  up  of  a  pulp,  a  wash-water,  and 
a  discharge  tank.  A  revolving  carriage  with  suitable  mechanism 
carries  14  trays  of  over  3  square  feet  area  each.  The  under  sides 
of  these  trays  or  plates  are  prepared  as  leaf  filters  with  vacuum 
and  compressed-air  attachments.  As  the  carriage  revolves  the 
trays  or  leaves  are  first  immersed  in  the  pulp,  through  which 
they  pass  and  from  which  they  are  mechanically  lifted  to  emerge 
with  a  cake  of  pulp  and  then  to  be  lowered  into  the  wash  solution 
through  which  they  pass.  Each  tray  is  finally  lifted  out  and 
brought  over  the  discharge  hopper,  where  the  vacuum  is  auto- 
matically cut  off  and  compressed  air  admitted  to  detach  the 
cake,  when  the  tray  again  passes  into  the  slime  pulp. 

The  Kelly,  as  shown  in  Fig.  27,  is  a  movable,  intermittent  pres- 
sure filter.  It  consists  of  a  long  boiler-like  tank  set  on  a  small 
incline.  The  lower  head  of  this  pressure  tank  is  fitted  with  a 
quick-acting  closing  device.  Upon  opening  the  clamp,  the  frame 
carrying  the  head  together  with  the  set  of  vertical  filter  leaves 
running  the  length  of  the  tank  may  be  run  out  of  the  tank  cham- 
ber, running  on  suitable  tracks  within  and  without  the  tank.  After 
dropping  in  the  usual  way  the  cake  adhering  to  the  leaves,  the 
carriage  now  lightened  by  the  removal  of  the  load  of  slime  can 
easily  be  drawn  into  the  pressure  tank  and  the  head  locked.  Pulp 
is  then  pumped  into  the  tank  under  suitable  pressure  which  may 
be  as  high  as  80  pounds  per  square  inch.  As  soon  as  the  air  has 
been  displaced  and  the  tank  is  consequently  full  of  the  pulp, 
the  cake  commences  to  form.  The  pressure  of  the  pump  acts 


FILTRATION 


149 


just  as  atmospheric  pressure  would,  except  that  on  account  of 
the  increased  pressure  the  cake  is  made  and  washed  in  a  com- 
paratively short  time.  The  pressure  of  the  pump  in  forming 
the  cake  causes  the  solution  expressed  and  filtered  out  of  the 


Wash  Solution  l-HUJStroug  Solution 
To  Vacuum  Pump 


Fig.  26.  —  Section  and  Plan  of  Ridgeway  Filter. 

pulp  to  pass  into  the  interior  of  the  leaves,  there  to  run  through 
suitable  pipes  out  of  the  press  into  the  solution  tank.  The 
cake  having  formed,  which  is  indicated  by  the  decrease  in  the 
solution  flowing  from  the  press,  pumping  pulp  into  the  tank 
under  pressure  is  stopped.  The  surplus  pulp  is  then  allowed 


150 


TEXT  BOOK  OF  CYANIDE  PRACTICE 


FILTRATION 


151 


to  run  from  the  filter  back  into  the  stock  tank,  being  displaced 
by  air  under  a  low  pressure  to  hold  the  cakes  in  place.  After 
the  surplus  pulp  has  been  removed,  wash  water  or  solution  is 
pumped  into  the  tank  and  continued  under  high  pressure  for 
as  many  minutes  as  experiments  have  indicated  are  required  to 
give  a  good  wash  or  to  pass  a  certain  volume  of  solution  through, 


Fig.  28.  —  Kelley  Filter  Presses,  and  Continuous  Agitation. 

when  the  surplus  solution  is  removed  in  the  same  manner  as 
the  surplus  pulp  was.  The  remaining  moisture  in  the  cake  is 
displaced  by  the  air  under  pressure  until  no  more  solution  runs 
from  the  press.  The  final  step  is  to  cut  off  the  air  pressure, 
and  unclamp  the  head  to  run  out  the  carriage  and  remove  the 
load  of  slime.  The  details  of  the  press  have  been  perfected  to 
such  an  extent  that  a  battery  of  four  presses  has  been  handled  by 
one  set  of  levers  and  valves,  and  two  batteries  of  four  presses 
each  have  been  tended  by  one  operator  and  a  helper. 


152 


TEXT  BOOK  OF  CYANIDE  PRACTICE 


The  Burt  rapid  filter  is  a  stationary,  intermittent  pressure 
filter.  It  is  somewhat  similar  to  the  Kelly,  except  that  the  filter 
leaves  are  suspended  vertically  at  right  angles  to  the  length  of 
the  tank,  which,  being  set  at  a  considerable  incline  that  the 
surplus  pulp  may  easily  run  to  the  outlet,  makes  the  leaves  in 
the  shape  of  an  elongated  circle.  These  leaves  are  only  removed 


Fig.  29.  —  The  Burt  Rapid  Filter. 

for  repairs,  consequently  the  slime  cake  is  discharged  by  intro- 
ducing air  and  water  into  the  interior  of  the  leaf  and  letting 
the  pulp  slide  out  through  a  discharge  opening. 

The  Burt  revolving  filter  is  a  revolving,  intermittent  pres- 
sure filter.  It  consists  of  a  long  revolving  shell  very  similar  to  a 
tube  mill  or  revolving  drier.  It  has  a  length  of  about  40  feet 
and  a  diameter  of  about  42  inches,  and  revolves  at  a  speed  of 
15  revolutions  per  minute.  The  interior  shell  of  the  cylinder 


FILTRATION 


153 


154          TEXT  BOOK  OF  CYANIDE  PRACTICE 

is  prepared  as  a  leaf-filtering  surface.  The  required  amount  of 
slime  pulp  for  a  charge  is  delivered  to  the  interior  of  the  filter 
through  a  valve  at  the  point  where  the  feed  is  delivered  to  a 
tube  mill.  After  the  charge  of  slime  has  been  admitted,  air 
under  a  pressure  of  25  to  45  pounds  is  turned  in.  The  liquid 
slime  pulp  remains  constantly  in  the  bottom  of  the  filter  through- 
out its  length  as  it  revolves.  The  air  pressure  causes  the  solu- 
tion to  pass  through  the  filter  cloth  and  out  through  holes  in 
the  shell  to  a  sump  over  which  the  filter  revolves.  The  pulp 
gradually  collects  as  a  shell  on  the  filter  surface.  When  the 
cake  has  been  made,  as  is  indicated  by  air  coming  out  of  the 
solution  discharges,  the  wash  solution  is  admitted  and  kept 
under  air  pressure.  As  the  tube  is  constantly  revolving  this 
results  in  a  very  good  washing  or  displacement  of  the  original 
gold  solution  in  the  pulp.  After  final  air  displacement  the  en- 
tire end  of  the  filter  is  opened  by  a  quick-acting  device.  The 
removal  of  the  air  pressure  causes  the  cake  to  fall  to  the  bottom 
of  the  cylinder,  and  the  addition  of  a  little  water  together  with 
the  revolving  of  the  filter  causes  the  washed  pulp  to  slide  out 
the  discharge  end;  when  the  end  gate  is  closed  and  a  new 
charge  started.  The  advantages  claimed  are  that  it  will  handle 
very  sandy  pulp,  requires  no  excess  pulp  or  solution  to  be  re- 
turned, gives  a  very  efficient  wash  through  its  method  of  making 
and  washing  a  cake,  and  requires  but  little  repairs  on  the  filtering 
medium. 

To  tabulate  these  illustrations  of  the  different  types  of  filters: 

Stationary  charge,  intermittent,  vacuum.     Butters. 

Movable  charge,  intermittent,  vacuum.     Moore. 

Movable  charge,  vertically  revolving,  continuous,  vacuum. 
Oliver. 

Stationary  charge,  horizontally  revolving,  continuous,  vac- 
uum. Hunt. 

Movable  charge,  horizontally  revolving,  continuous-inter- 
mittent, vacuum.  Ridgeway. 

Movable  charge,  intermittent,  pressure.     Kelly. 

Stationary  charge,  intermittent,  pressure.     Burt  rapid  filter. 

Movable  charge,  vertically  revolving,  intermittent,  pressure. 
Burt  revolving  filter. 

The  leaf  filter  in  many  cases  is  more  efficient  than  the  plate 
and  frame  filter  press,  and  is  much  cheaper  to  operate,  excepting 


FILTRATION  155 

the  Merrill  press,  which  when  used  with  the  "  center-washing  " 
system  may  be  considered  as  another  type  of  the  leaf  filter. 
Leaf  filters  are  especially  efficacious  in  handling  a  clayey  slime 
that  the  plate  and  frame  press  cannot  wash  or  only  with  diffi- 
culty, and  by  the  "  center- washing "  process.  This  is  due 
mainly  to  the  inability  to  wash  such  a  slime  cake  2  or  3  inches 
thick,  whether  made  in  the  plate  and  frame  press  or  in  the 
leaf  filter.  However,  the  leaf  filters  are  far  from  being  per- 
fect and  able  to  handle  all  classes  of  material,  consequently 
while  they  are  in  most  cases  the  best  device  available,  the  par- 
ticular one  to  be  used  should  be  selected  with  great  care,  bear- 
ing in  mind  its  limitations  and  the  conditions  with  which  it 
must  cope. 

One  of  the  first  troubles  encountered  is  the  necessity  of  having 
a  slime  that  contains  a  considerable  amount  of  granular  mate- 
rial to  give  porosity  to  the  cake  and  enable  a  thick  and  easily- 
washed  charge  or  cake  to  be  made.  This  is  a  condition  which 
is  not  hard  to  meet,  but  the  necessity  of  this  granular  material 
being  extremely  fine  may  work  a  hardship  where  all  of  the  ore 
is  being  treated  as  a  slime,  in  requiring  the  ore  to  be  crushed 
far  beyond  the  economic  point  that  will  allow  a  high  dissolution 
of  the  precious  metals.  As  the  amount  of  sand  or  granular 
material  increases,  the  slime  becomes  less  plastic  and  more 
permeable  by  the  wash  solution,  consequently  with  a  true  slime 
a  cake  of  only  j  to  ^  inch  may  be  possible,  but  as  the  amount 
of  sand  increases,  a  cake  up  to  2  inches  and  even  more  may 
be  made.  Besides  the  increase  in  capacity  that  the  sandier 
charge  gives,  there  is  invariably  a  quicker  and  better  washing. 
But  an  increase  in  the  amount  of  sand  or  its  coarseness  increases 
the  inability  to  make  a  good  cake  and  give  all  the  pulp  a  good 
washing,  for  as  the  pulp  supplied  to  the  filters  becomes  more 
dilute  and  the  sand  becomes  larger  in  quantity  and  coarser, 
the  pulp  classifies  more  in  the  making  of  a  cake  through  the 
settling  of  the  sand.  This  introduces  difficulties  into  the  making 
and  washing  of  a  cake  and  removing  the  pulp,  even  though  the 
principle  of  the  cakes  being  built  up  with  an  even  permeability 
works  admirably.  That  coarse  sand  which  settles  in  the  corners 
and  bottoms  of  the  filter  tanks  especially  gives  trouble.  It  has 
been  attempted,  without  entire  success,  to  stop  this  classifying  in 
the  stationary  vacuum  type  by  pumping  the  thicker  sand  set- 


156  TEXT  BOOK  OF  CYANIDE  PRACTICE 

tling  to  the  bottom  of  the  filter  to  the  top  as  the  cake  forms. 
With  the  movable  vacuum  type  the  pulp  is  kept  in  agitation 
usually  by  air,  causing  the  formation  of  considerable  carbonate 
of  lime  which  closes  the  pores  of  the  filter  cloths.  In  both 
cases  there  is  trouble  with  pulp  containing  a  large  amount  of 
coarse  sand.  The  pressure  filter  is  able  to  handle  this  material 
much  better  than  the  vacuum  or  atmospheric-pressure  filter,  for 
by  reason  of  the  higher  pressure  used  (up  to  80  pounds)  as 
against  the  atmospheric  pressure  (up  to  15  pounds)  a  cake  can 
be  made  in  the  pressure  filter  in  10  minutes,  including  filling 
and  emptying,  that  will  require  from  40  minutes  to  1J  hours  to 
make  with  the  vacuum  filter.  The  higher  the  specific  gravity 
of  the  pulp,  the  more  viscous  and  dense  it  is,  and  the  larger  the 
amount  of  dry  pulp  in  it,  the  better  it  can  be  worked,  for  the 
larger  the  amount  of  dry  pulp  and  true  slime  the  better  it  will 
hold  the  slime  and  sand  in  suspension  and  prevent  classifying. 
When  containing  but  little  sand  and  that  very  fine,  a  dilute  pulp 
may  be  used,  but  as  the  sand  becomes  greater  in  quantity  and 
coarser  the  pulp  must  be  thickened.  The  advantage  of  the 
pressure  filter  over  the  vacuum  type  in  making  quick  charges 
on  this  class  of  material  —  pulp  containing  much  sand  —  is  pro- 
nounced. 

The  pressure  filters  have  the  disadvantage  of  small  capacity 
per  charge  which  they  overcome  to  some  extent  by  the  rapidity 
with  which  the  charges  are  made,  but  this  requires  that  much 
additional  attention.  The  intermittent-vacuum  filters  can  be 
built  with  enormous  capacities,  which  reduce  the  amount  of 
labor  required  per  ton  treated  considerably  over  the  pressure 
type.  The  movable-pressure  filter  has  the  advantage  over  the 
stationary  type,  of  each  charge  being  exposed  to  view  after  the 
washing,  so  that  it  is  possible  to  know  just  how  the  operations 
are  proceeding  and  take  steps  to  overcome  any  acute  difficulties, 
as  well  as  allow  repairs  to  be  easily  made.  It  probably  gives 
the  most  efficient  washing  of  all  the  types  of  filters,  but  requires 
more  manipulation  than  the  others.  Intermittent-pressure  fil- 
ters can  be  installed  in  small  plants  cheaper  than  the  intermit- 
tent-vacuum filters,  but  are  not  so  suitable  in  first  cost  and 
operating  expenses  for  large  plants. 

The  Ridgeway,  in  which  the  charge  revolving  horizontally  is 
immersed  in  the  wash  solution,  appears  to  give  the  most  efficient 


FILTRATION  157 

wash  of  the  continuous  filters,  but  has  the  disadvantage  of  low 
capacity  and  extreme  delicatehess.  Those  filters,  whether  con- 
tinuous or  otherwise,  that  wash  by  means  of  a  spray  cannot  be 
considered  as  such  efficient  washers  as  those  in  which  the  cake 
is  washed  by  submersion,  but  have  the  advantage  of  simplicity, 
requiring  little  attention,  and  simplifying  the  operations  gener- 
ally. The  Oliver,  the  revolving-drum  filter,  appears  to  be  well 
adapted  and  working  largely  at  present  on  filtering  a  true  slime, 
a  material  that  other  filters  have  not  yet  satisfactorily  handled. 
The  Hunt  and  similar  filters,  as  horizontally-revolving  mechan- 
isms treating  sand  or  slime,  would  appear  to  be  well  adapted  to 
treating  a  pulp  containing  a  large  amount  of  coarse  granular 
material.  Apparently  coarse  sand  is  best  treated  by  a  mechan- 
ism in  which  gravity  assists  in  holding  the  sand  at  the  point 
where  it  is  attached  to  the  filter,  as  on  the  bed  of  a  horizontal 
filter.  Continuous  filters  have  the  advantage  of  requiring  little 
attention,  whereas  all  intermittent  ones  require  continuous  at- 
tendance. Like  pressure  filters  their  small  capacity  well  adapts 
them  for  small  plants,  but  not  so  well  for  large  plants.  Another 
advantage  of  the  continuous  filters  is  that  the  costly  item  of 
returning  the  surplus  pulp  from  the  stationary-vacuum  filters, 
moving  the  filter  basket  in  the  movable-vacuum  type  with  its 
complicated  machinery  and  wear  and  chance  for  breakage,  or 
the  pumping  against  pressure  in  the  pressure  type,  is  avoided 
in  the  continuous  filter  which  takes  by  gravity  the  feed  of  pulp 
at  a  constant  rate.  A  great  advantage  of  the  continuous  over 
the  intermittent  system,  in  which  the  surplus  wash  solution  is 
returned  to  its  stock  tank,  is  that  there  is  no  "  building  up  "  in 
the  value  of  the  solution.  When  the  surplus  wash  solution  is 
returned  from  a  filter  tank,  it  is  richer  than  when  it  entered, 
through  its  contact  with  the  rich  solution  of  the  unwashed  pulp 
as  found  in  the  pipes,  the  bottom  and  sides  of  the  filter  tank, 
and  in  the  cakes  themselves.  Likewise  in  wash-solution  tanks 
after  the  movable  leaves  have  been  introduced  and  removed, 
though  undoubtedly  not  to  the  extent  where  the  unwashed 
pulp  and  the  wash  solution  enter  and  are  withdrawn  from  the 
same  box  or  tank.  The  value  in  the  wash  solution  builds  up 
rapidly  in  this  way  and  would  soon  approach  that  of  the  solution 
in  the  slime  cakes  as  first  formed,  were  it  not  that  this  solution  is 
sent  to  the  zinc  boxes  as  soon  as  its  value  mounts  to  a  certain 


158  TEXT  BOOK  OF  CYANIDE  PRACTICE 

figure.  This  is  one  of  the  principal  weaknesses  of  the  leaf- 
filter  process  and  is  a  source  of  great  mechanical  loss  of  the  dis- 
solved precious  metals.  Some  plants  keep  down  this  loss  by 
constantly  washing  with  barren  solution,  returning  the  surplus 
to  the  crushing  department  or  elsewhere,  but  this  involves  the 
precipitation  of  a  large  amount  of  solution  and  generally  results 
in  a  high  mechanical  and  .other  loss  of  cyanide,  through  the  im- 
possibility of  segregating  a  low-strength  solution  for  filter  wash- 
ing and  for  crushing. 

The  filter  cloths  of  all  filters  using  the  leaf  filter  or  "  center- 
washing  "  system  are  subjected  to  being  encrusted,  coated,  or 
clotted  by  a  carbonate  of  lime,  much  of  which  results  from  the 
action  of  air  used  in  agitation  upon  the  lime  in  solution,  and  in 
some  silver  plants  has  caused  the  protective  alkalinity  to  be 
kept  lower  than  otherwise  desired.  This  coating,  in  spots  and 
generally,  reduces  the  permeability  of  the  cloth  or  increases  its 
resistance  to  the  flow  of  solution  through  it,  so  that  a  thinner 
cake  is  formed  than  usual  and  the  capacity  is  reduced.  The 
deposit  of  lime  is  removed  by  immersing  the  leaves  in  a  \  to 
2  per  cent  solution  of  hydrochloric  acid,  which  removes  the 
lime  as  a  chloride.  The  item  for  the  removal  of  the  lime  by 
treating  the  leaves  is  quite  large  with  some  types  of  filters. 
With  the  pressure  and  plate  and  frame  types  the  acid  wash  may 
be  pumped  through  the  press,  but  with  the  other  types  the 
leaves  must  be  removed  or  other  means  employed,  involving 
considerable  labor. 

The  type  of  filter  to  be  installed  is  a  matter  of  personal  opinion. 
All  have  their  good  and  bad  features,  each  is  well  adapted  for 
certain  conditions  and  poorly  for  others.  That  none  of  them  is 
perfect  or  is  the  acme  of  what  is  to  be  desired,  is  a  matter  of 
universal  knowledge,  and  is  indicated  by  the  number  of  promi- 
nent plants  that  use  their  modern  filters  as  dewaterers,  without 
attempting  to  give  the  pulp  any  wash. 


CHAPTER  XII 
PRECIPITATION 

THE  cyanide  solution  carrying  gold  and  silver,  in  which  con- 
dition it  is  often  called  "  pregnant  "  or  "  gold  "  solution,  having 
been  removed  from  the  ore  by  draining  the  percolation  charge 
if  a  sand  or  leaching  plant,  by  decanting  the  clear  supernatant 
solution  from  the  settled  slime  if  a  decantation  plant,  or  by 
forcing  the  solution  from  the  pulp  through  a  filter  cloth  or  other 
medium  if  the  slime  pulp  is  finally  filtered,  is  conveyed  to  the 
gold  tanks  to  be  supplied  to  the  precipitating  department  as 
needed.  This  solution  after  precipitation  is  called  "  barren  " 
solution.  Outside  of  a  few  plants  where  electrical  precipitation 
is  used  on  silver  ores,  and  which  appears  to  be  assisted  by  zinc 
boxes  where  a  close  precipitation  of  the  gold  is  required,  zinc  is 
universally  used  as  a  precipitant,  either  in  the  form  of  threads 
or  shavings  or  as  a  fume  or  dust. 

Reactions  in  Zinc  Precipitation  and  Formation  of  White  Pre- 
cipitate. —  -  The  precipitation  of  the  precious  metals  may  be 
said  to  be  due  to  the  replacement  of  the  gold  and  silver  in  the 
double  cyanide  by  the  zinc  and  to  electric  currents  set  up  by  the 
chemical  reactions  which  electrochemically  deposit  the  precious 
metals  from  the  solution.  Other  theories  have  been  advanced 
and  undoubtedly  have  some  weight,  but  the  above  is  both  more 
acceptable  and  more  illustrative  of  the  principles  and  practice 
of  precipitation. 

The  precipitation  of  gold  and  similarly  of  silver  in  the  presence 
of  free  cyanide  may  be  expressed  in  the  equation: 
KAu(CN)2  +  2KCN+Zn+H2O=K2Zn(CN)4  +  Au+H-hKOH. 
In  the  absence  of  free  cyanide  as : 

KAu(CN)2  +  Zn  +  H2O  =  Zn(CN)2  +  Au  +  H  +  KOH. 
The  following  reaction  may  take  place  in  the  absence  of  any 
metal  to  be  precipitated: 

Zn  +  4  KCN  +  2  H2O  =  K2Zn(CN)4  +  2  H  +  2  KOH. 

159 


160  TEXT  BOOK  OF  CYANIDE  PRACTICE 

Alkalis  act  upon  zinc  to  form  an  alkaline  zincate,  as: 

Zn  +  2  KOH  =  Zn(OK)2  +  2  H. 

While  the  alkaline  zincate  may  be  dissolved  in  free  cyanide,  as: 
Zn(OK)2  +  4  KCN  +  2  H2O  =  K2Zn(CN)4  +  4  KOH. 

Zinc  oxide  (ZnO)  formed  through  exposure  of  the  zinc  to  the 
atmosphere,  especially  when  the  zinc  is  moist,  may  be  changed 
to  zinc  hydroxide  (Zn(OH)2),  or  the  zinc  hydroxide  may  be 
formed  directly,  as: 

f  ZnO  +  H2O  =  Zn(OH)2. 

( Zn  +  2  H2O  =  Zn(OH)2  +  H2. 

Zinc  oxide  or  hydroxide  may  be  formed  in  a  similar  way  by  the 
oxidizing  effect  of  a  solution  without  free  cyanide  or  alkali  to 
combine  with  the  zinc.  The  oxide  or  hydroxide  may  be  changed 
to  the  zincate  by  an  alkali,  as: 

f  ZnO  +  2  KOH  =  Zn(OK)2  +  H2O. 
(Zn(OH)2  +  2  KOH  =  Zn(OK)2  +  2  H2O. 

In  the  presence  of  free  cyanide  the  oxide  or  hydroxide  may  be 
changed  to  the  potassium  zinc  cyanide,  as: 

(ZnO  +  H20)  +  4  KCN  =  K2Zn(CN)4  +  2  KOH. 

The  law  of  mass  action  undoubtedly  prevails  to  make  some  of 
the  above  reactions  reversible. 

The  tendency  is  strong  for  the  double  cyanide  of  zinc,  the 
zinc  potassium  cyanide  (K2Zn(CN)4),  to  disassociate  in  a  weak 
cyanide  solution  into  the  simple  cyanides,  as:. 

K2Zn(CN)4  =  2  KCN  +  Zn(CN)2. 

Zinc  cyanide  (Zn(CN)2)  is  insoluble  in  water,  hence  in  very  dilute 
cyanide  solutions  it  precipitates  to  form  the  white  precipitate 
of  the  zinc  boxes.  Zinc  cyanide  is  dissolved  and  reacted  upon 
by  alkali,  as: 

|Zn(CN)2  +  4  KOH  =  2  KCN  +  Zn(OK)2  +  2  H2O. 

[2  Zn(CN)2  +  4  KOH  =  K2Zn(CN)4  +  Zn(OK)2  +  2  H20. 

As  both  the  zinc  potassium  cyanide  and  the  potassium  zincate 
(Zn(OK)2)  are  soluble  in  water  and  still  more  so  in  alkaline 
solutions,  the  white  precipitate  appears  to  a  slight  extent  only 
in  strongly  alkaline  solutions,  even  though  weak  in  cyanide. 


PRECIPITATION  161 

The  dissolved  zinc  or  the  zinc  oxide  eventually  forming  zinc 
hydroxide  (Zn(OH)2)  is  acted  Upon  by  free  cyanide,  as: 

Zn(OH)2  +  4  KCN  =  K2Zn(CN)4  +  2  KOH. 

Thus  the  zinc  oxide  or  hydroxide  which  is  insoluble  in  water 
and,  in  consequence,  in  a  very  weak  cyanide  solution  will  precipi- 
tate to  form  the  white  precipitate  of  the  zinc  boxes;  in  a  solution 
strong  in  cyanide  will  form  the  soluble  double  potassium  or 
other  alkaline  zinc  cyanide;  or  in  a  solution  strong  in  alkali 
will  form  the  soluble  potassium  or  other  alkaline  zincate. 

Clarifying  the  Solution.  —  If  there  is  a  tendency  for  the  solu- 
tion to  leave  the  sand  vats  or  agitation  tanks  carrying  consid- 
erable suspended  matter  or  slime  which  would  interfere  with 
precipitation,  the  solution  may  be  filtered  before  or  after  the 
gold  tanks  by  means  of  sand  filters.  These  consist  of  boxes  or 
small  tanks  with  filter  bottoms  similar  to  those  of  leaching  vats, 
except  that  the  filter  cloth  is  very  porous,  usually  coarse  burlap. 
This  is  covered  with  about  twelve  inches  of  coarse  sand.  The 
solution  filtering  through  leaves  its  slime  covering  the  sand, 
where  it  may  be  periodically  scraped  off.  Or  the  solution  may 
be  introduced  into  the  bottom  of  the  gold  tank  by  means  of  a 
pipe  or  baffle  board,  and  syphoned  off  the  top  for  precipitation 
in  a  much  clearer  and  more  settled  state.  Plate  and  frame 
filter  presses  have  also  been  used  for  clarifying  purposes. 

Zinc  Boxes.  —  Zinc  boxes  for  holding  the  zinc  shavings  are 
arranged  that  the  solution  may  in  all  cases  flow  upward  through 
the  shavings.  This  gives  better  results  than  a  downward  flow 
for  several  reasons.  It  permits  an  easier,  gentler,  and  better- 
distributed  movement  of  the  solution  as  it  rises  upward  through 
the  zinc.  It  allows  the  partly  consumed  and  better  precipitat- 
ing zinc  in  the  bottom  of  each  compartment  to  come  in  contact 
with  the  solution  before  the  newer  zinc,  giving  more  effective 
precipitation,  greater  economy  in  zinc,  and  less  trouble.  It 
causes  less  disturbance  in  dressing  the  boxes  of  the  fine  gold  and 
silver  slime  adherent  or  fallen  from  the  zinc.  The  upward  move- 
ment assists  the  hydrogen  bubbles  formed  to  naturally  rise  and 
become  liberated  instead  of  adhering  to  the  zinc,  coating  and 
fouling  it  against  precipitation. 

In  the  bottom  of  each  compartment  is  placed  a  screen  or 
false  bottom  from  three  to  six  inches  above  the  floor  or  bottom 


162 


TEXT  BOOK  OF  CYANIDE  PRACTICE 


of  the  zinc  box.  This  screen  may  vary  from  4  to  12-mesh.  It 
serves  to  hold  the  zinc  some  distance  from  the  bottom  of  the 
box  that  the  solution  may  easily  reach  the  entire  lower  area  of 
the  zinc  shavings  to  rise  evenly  throughout  the  mass,  and  that 
the  space  below  the  screen  may  act  as  a  retainer  for  the  fine 
gold  and  silver  slime  falling  off  the  zinc  and  passing  through  the 
screen.  The  first  compartment  of  the  box  is  often  used  as  a 


Fig.  31.  —  Zinc  Box. 

settler  to  assist  in  clarifying  the  solution  by  having  no  zinc  placed 
in  it;  while  the  last  compartment  may  be  used  in  a  similar 
way  to  prevent  fine  gold-silver  slime  from  being  carried  away 
when  the  box  is  disturbed  or  the  flow  is  too  great.  Often  a 
filter  of  coarse  sand,  sawdust,  oakum,  fiber  packing,  or  coarse 
filter  cloth  is  used  in  these  end  compartments.  The  filtering 
medium  in  the  last  compartment  is  eventually  added  to  the  zinc 
slime  melted  to  get  any  gold-silver  slime  which  it  may  have 
caught. 

Zinc  boxes  vary  considerably  in  size.     The  larger  sizes  should 


PRECIPITATION  163 

always  be  used  to  secure  economy  of  space  and  care.  A  good 
size  for  a  large  box  would  be  to  consist  of  eight  compartments 
for  upward  flow,  each  21  inches  long  (in  direction  of  flow),  27 
inches  wide  (across  box),  and  33  inches  deep  above  the  screens. 
Each  compartment  of  this  box  will  hold  approximately  10  cubic 
feet  of  zinc  shaving.  The  six  compartments,  allowing  the  end 
ones  for  settling  purposes,  will  contain  a  total  of  60  cubic  feet. 
The  majority  of  zinc  boxes  are  built  with  their  compartments 
in  the  form  of  a  perfect  cube  or  nearly  so. 

Size  of  Shavings.  —  The  important  point  in  zinc  precipita- 
tion is  the  necessity  of  exposing  a  large  area  of  zinc  to  the  solu- 
tion. Consequently  to  get  the  highest  efficiency  from  the  zinc, 
it  is  prepared  as  a  fine  dust  or  in  shaving  or  threads  ^  to  I  inch 
wide  and  from  4^  to  ysW  inch  in  thickness.  A  pound  of 
shavings  cut  with  a  thickness  of  yyVer  inch  will  expose  about 
80  square  feet  of  zinc  surface,  and  when  cut  with  a  thickness 
of  T$-Q  inch  will  give  about  40  square  feet  of  zinc  surface.  This 
will  indicate  why  equal  weights  of  the  finer-cut  shaving  will 
precipitate  better  than  those  cut  coarser.  Some  idea  of  how 
zinc  becomes  effective  through  fine  division  can  be  seen  when 
it  is  said  that  a  pound  of  zinc  equals  3.854  cubic  inches,  and 
when  cut  into  shaving  and  placed  in  the  boxes  at  the  rate  of 
6  to  8|  pounds  per  cubic  foot,  the  solid  metal  amounts  to  only 
1.3  to  1.9  per  cent  of  the  space  actually  occupied  by  the  zinc 
shavings.  How  fine  a  shaving  should  be  used  must  be  deter- 
mined by  actual  practice.  The  coarsest  shaving  that  will  give 
a  satisfactory  precipitation  should  be  employed,  as  the  coarser 
the  shaving  the  slower  it  will  be  to  break  up  into  short  zinc 
which  entails  a  higher  mechanical  loss  when  gathered  into  the 
clean-up  and  greater  trouble  in  operating  and  dressing  the  boxes. 
A  thickness  of  T£FG  mcn  is  generally  used  in  gold  plants,  and 
from  T^j  to  T/(ytf  inch  in  silver  plants. 

Weight  of  Shaving  and  Amount  Required.  —  The  weight  of 
a  cubic  foot  of  finely-cut  zinc  shaving  when  packed  in  the 
boxes,  in  the  customary  manner  in  gold  plants,  will  vary  from  6 
to  8J  pounds,  depending  upon  their  thickness  and  how  snugly 
and  tightly  they  are  packed  in.  With  the  coarser-cut  shaving 
a  greater  weight  of  zinc  may  be  packed  in  a  cubic  foot,  both 
because  the  greater  thickness  of  the  threads  gives  a  greater 
weight  of  zinc  in  comparison  to  the  voids,  and  because  the 


164  TEXT  BOOK  OF  CYANIDE  PRACTICE 

thicker  and  stronger  threads  or  shaving  may  be  more  tightly 
packed  in  the  boxes  without  being  easily  broken  and  channeled 
by  the  solution.  Silver  plants  using  coarser  shaving  pack  12 
to  13  pounds  of  zinc  per  cubic  foot.  It  is  reported  that  as  high 
as  18  to  23  pounds  of  zinc  per  cubic  foot  have  been  packed  in 
the  boxes  in  an  experimental  way. 

In  gold  plants  it  is  customary  to  allow  1  cubic  foot  of  zinc- 
box  space  for  each  ton  of  solution  to  be  precipitated  in  24  hours. 
The  rate  of  flow  in  the  average  gold  plant  is  probably  a  little 
higher  than  this;  in  some  it  reaches  over  2  tons  per  24  hours  for 
each  cubic  foot  of  zinc  shaving.  In  silver  plants  the  rate  of 
flow  will  vary  from  1  to  6  tons  of  solution  per  24  hours  for  each 
cubic  foot  of  zinc  shaving;  probably  1J  to  3  tons  would  repre- 
sent the  average  practice.  The  higher  rate  of  flow  in  silver 
plants  is  due  to  the  stronger  solution  used  causing  more  effective 
precipitation,  and  to  the  fact  that  the  efficiency  of  the  precipi- 
tation, as  referring  to  the  weight  of  precious  metal  still  remaining 
unprecipitated  in  the  solution,  need  not  be  as  great  as  in  gold 
precipitation.  A  flow  of  1  ton  per  cubic  foot  of  zinc  per  24 
hours  gives  a  contact  between  the  solution  and  the  shaving  of 
about  45  minutes. 

The  number  of  compartments  to  be  filled  with  zinc  will  de- 
pend upon  the  tonnage  put  through  the  boxes  and  the  effective- 
ness of  the  precipitation.  No  more  zinc  should  be  kept  in  the 
boxes  than  is  necessary  to  secure  good  precipitation,  or  zinc 
will  be  consumed  unnecessarily.  It  hardly  appears  necessary  to 
have  more  than  one  or  possibly  two  lower  compartments,  in 
which  the  new  zinc  is  added,  containing  bright  zinc.  If  the 
zinc  in  too  many  of  the  lower  compartments  remains  bright  and 
assays  of  solution  taken  from  the  different  compartments  show 
that  the  precious  metals  are  all  precipitated  in  the  upper  com- 
partments, either  some  of  the  lower  compartments  should  be 
left  empty  or  the  flow  should  be  increased  to  the  point  where 
the  filled  compartments  are  working  at  a  proper  efficiency.  In 
short,  under  normal  conditions  it  is  the  rate  of  flow  per  cubic 
foot  of  zinc  that  must  be  kept  constant.  If  the  flow  through 
the  boxes  is  increased,  the  number  of  cubic  feet  of  zinc  must  be 
increased.  If  the  flow  is  decreased,  the  number  of  cubic  feet 
of  zinc  may  be  lessened.  It  is  also  necessary  in  studying  con- 
ditions or  making  comparisons  to  remember  that  under  equal 


PRECIPITATION  165 

conditions  the  effectiveness  of  the  precipitation  depends  upon 
the  area  of  zinc  exposed  person  or  unit  of  solution,  and  that 
the  thickness  of  the  shaving  and  the  quantity  or  weight  per 
cubic  foot  as  packed  are  just  as  important  factors  in  giving  the 
zinc  area  as  the  number  of  cubic  feet  of  packed  shaving  used. 

Packing  and  Dressing  the  Boxes.  —  It  is  necessary  in  packing 
the  boxes  with  zinc  shaving  to  take  the  greatest  care  to  prevent 
channeling  and  an  uneven  flow  through  the  zinc.  The  use  of 
a  number  of  compartments,  through  each  of  which  the  solution 
must  flow,  reduces  the  danger  of  poor  precipitation  from  this 
cause.  Taking  the  case  of  a  clean-up  of  the  gold-silver  slime 
being  made  to  illustrate  the  method  of  caring  for  the  boxes, 
after  the  compartment  has  been  washed  clean  of  all  slime 
through  a  hole  in  the  bottom  emptying  into  a  launder,  the  dis- 
charge is  closed  and  the  screen  put  in  place.  New  zinc  is  now 
taken,  preferably  that  cut  a  little  coarser  than  as  ordinarily 
used.  This  is  fluffed  by  gently  pulling  apart  and  untangling  the 
bunches,  especially  the  more  compact  ones,  and  is  placed  evenly 
over  the  screen  to  the  depth  of  a  few  inches.  On  top  of  this  is 
spread  an  even  layer  of  the  short  zinc  being  returned  to  the 
boxes,  then  a  layer  of  the  long  zinc  being  returned,  to  be  fol- 
lowed by  a  layer  of  the  short  zinc,  and  so  on  until  the  compart- 
ment is  filled.  The  purpose  of  the  coarse  new  zinc  is  to  act  as 
a  screen  as  long  as  it  is  able  to  withstand  the  dissolving  action, 
to  diffuse  the  solution  passing  up  through  it,  and  to  utilize  the 
short  zinc  even  after  it  is  well  eaten  up  by  catching  and  holding 
it,  instead  of  allowing  it  to  drop  and  pass  through  or  clog  the 
screen.  The  compartments  being  used  are  packed  in  this  man- 
ner; the  short  zinc  and  that  already  much  acted  upon  are  con- 
centrated in  the  first  two  or  three  compartments.  After  the 
short  zinc  is  utilized,  the  already-acted-upon  long  zinc  is  used, 
and  finally  whatever  new  zinc  is  needed  is  placed  in  the  lower 
compartments.  The  fluffing  of  the  zinc  and  its  arrangement 
together  with  the  placing  of  the  layers  of  short  zinc  must  be 
studied  with  a  view  to  preventing  channeling  and  an  uneven  flow. 

The  boxes  should  be  dressed  as  frequently  as  needed,  which 
is  usually  every  second  or  third  day.  The  necessity  of  dressing 
and  how  often  it  should  be  done  can  be  studied  from  three 
points:  the  increase  in  the  assays  of  the  solution  leaving  the 
box,  the  amount  of  zinc  consumed  and  extent  of  channeling, 


166  TEXT  BOOK  OF  CYANIDE  PRACTICE 

and  the  gradual  creeping  down  of  the  blackening  and  discol- 
oration of  the  bright  new  zinc  in  the  lower  compartment  or 
compartments  by  the  gold  and  silver  precipitated.  Small  lots 
of  new  shaving  may  be  placed  in  the  lower  compartments  to 
experimentally  observe  the  progress  of  discoloration. 

In  dressing  the  boxes  between  clean-ups,  the  flow  is  first 
turned  off  and  the  operator  begins  work,  using  a  pair  of  rubber 
gloves  or  with  hands  and  arms  greased  with  vaseline  or  other 
harmless  grease  compound  to  keep  the  skin  from  becoming 
rough,  irritated,  and  sore  by  contact  with  the  solution.  He 
either  moves  the  zinc  from  the  lower  compartments  to  the 
upper  ones,  where  practically  all  of  the  consumption  has  taken 
place,  adding  the  new  zinc  to  the  lower  compartments,  or  adds 
new  zinc  to  whatever  compartments  are  in  need  without  mov- 
ing any  of  the  old  zinc.  It  is  preferable  to  move  the  zinc  toward 
the  head  compartments  and  add  the  new  zinc  at  the  foot  of  the 
box,  as  zinc  that  has  already  been  acted  upon  is  a  more  active 
precipitant  than  new  zinc,  and  by  moving  it  toward  the  head  of 
the  boxes  it  causes  a  greater  precipitation  in  these  head  com- 
partments and  collects  that  occurring  in  the  balance  of  the  box 
into  them.  Moving  the  zinc  up  gives  a  better  precipitation, 
a  higher-grade  slime,  and  a  concentration  of  the  gold  and  silver 
into  a  smaller  area  of  the  box,  making  the  clean-up  less  bulky 
and  leaving  less  gold  and  silver  in  the  box.  In  moving  the  zinc 
up,  the  well-acted-upon  and  rotten  zinc  should  be  disturbed 
as  little  as  possible.  Most  of  the  precipitation  can  be  effected 
and  collected  in  the  first  two  or  three  compartments.  These 
should  be  disturbed  as  little  as  possible,  the  operator  confining 
himself  to  closing  up  any  channels  or  open  edges  or  corners, 
and  placing  the  necessary  zinc  taken  from  the  third  or  fourth 
and  lower  compartments.  No  zinc  should  be  removed  from  any 
compartment  in  which  such  an  amount  of  precipitation  takes 
place  that  the  shaving  becomes  rotten  and  tends  to  break  up 
in  handling,  as  it  causes  a  greater  mechanical  loss  and  disturbs 
the  gold-silver  slime,  rendering  it  more  liable  to  be  carried  out 
of  the  box.  The  zinc  should  be  spread  out  and  laid  down  in 
layers,  which,  being  at  right  angles  to  the  movement  of  the 
solution,  conduce  to  allow  an  even  flow  and  contact.  The  zinc 
should  be  well  packed  into  the  edges  and  corners  of  the  compart- 
ments, as  the  greatest  channeling  occurs  at  these  places.  A 


PRECIPITATION  167 

little  experience  and  study  will  soon  indicate  the  best  procedure. 
The  practice  of  beating  the  zmc  tightly  into  the  compartments 
with  a  stick  is  inadvisable,  since  it  may  pack  the  zinc  too  tightly 
for  a  uniform  flow.  Yet  the  zinc  should  be  firmly  and  carefully 
and  not  loosely  packed  in  place.  In  some  cases  the  zinc  when 
being  cut  has  been  folded  into  skeins  or  hanks  the  length  of  the 
compartments.  The  skeins  are  packed  into  the  compartments 
in  layers  at  right  angles  to  each  other,  new  zinc  being  added  as 
needed  without  disturbing  the  old  zinc.  This  method  tends  to 
give  a  more  uniform  flow  with  less  channeling. 

General  Care  of  Precipitation.  —  The  boxes  may  be  allowed 
to  stand  for  15  minutes  after  dressing  before  starting  the  flow 
through,  for  the  purpose  of  settling  any  disturbed  zinc  slime. 
The  highest  rate  of  flow  can  only  be  determined  by  assaying 
the  solution  as  it  leaves  the  box  and  observing  the  progress  of 
discoloration  of  the  bright  zinc  in  the  lower  compartments,  but 
must  not  be  so  rapid  as  to  carry  the  fine  zinc  slime  out.  It 
must  be  remembered  in  determining  this  that  the  best  precipi- 
tation takes  place  after  the  boxes  have  been  newly  dressed  and 
more  especially  after  a  clean-up,  when  the  zinc  is  clean,  active, 
and  well-arranged;  while  it  reaches  its  poorest  just  before  dress- 
ing and  cleaning-up.  The  maximum  efficiency  of  precipitation 
takes  place  when  an  equal  volume  of  solution  passes  by  each 
part  of  the  zinc,  which  is  when  the  zinc  is  newly  arranged. 
This  efficiency  rapidly  lessens,  for  channeling  quickly  forms 
whereby  the  solution  is  not  brought  evenly  in  contact  with  all 
the  zinc,  which  must  be  met  by  rearranging  the  zinc  through  a  new 
dressing  of  the  box.  Solution  strong  in  cyanide  keeps  the  zinc 
clean  and  active  and  gives  a  good  precipitation,  consequently  it 
can  be  run  through  the  boxes  much  faster  than  weak  solution. 

One  of  the  evidences  of  good  precipitation  is  the  rising  to  the 
surface  of  the  bubbles  of  hydrogen  which  are  generated  during 
the  precipitation,  as  is  shown  in  the  equation  representing  the 
process  of  precipitation.  Too  many  bubbles  given  off  are  un- 
desirable, for  it  indicates  a  large  consumption  of  zinc.  Strong 
cyanide  solutions  cause  a  large  evolution  of  hydrogen  through 
the  excessive  dissolution  of  the  zinc.  Too  high  a  protective 
alkalinity  will  act  similarly,  and  besides  consuming  an  unnec- 
essary amount  of  zinc  may  give  rise  to  excessive  hydrogen 
which  may  cling  to  and  lift  the  zinc  out  of  the  boxes  or  which 


168  TEXT  BOOK  OF  CYANIDE  PRACTICE 

may  polarize  it  against  effective  precipitation.  Where  the  zinc 
has  been  fouled  in  this  way,  a  low  strength  of  solution  may  be 
run  through  rather  fast,  followed  by  shaking  and  rearranging 
the  zinc.  An  excess  of  lime  or  alkali  may  cause  a  deposit  of 
lime  salts  or  other  compounds  as  a  species  of  white  precipitate. 
Where  slime  from  the  ore  has  been  carried  into  the  boxes,  or 
lime  salts  and  other  compounds  have  formed  loose  deposits  or 
incrustations, — such  deposits  as  cannot  be  dissolved  and  washed 
out  by  solutions  strong  in  cyanide  and  alkalinity,  —  and  good 
precipitation  cannot  be  secured,  the  boxes  should  be  cleaned  up. 
In  some  cases  the  incrustations  have  been  removed  by  dipping 
the  shavings  in  dilute  acid  to  dissolve  the  deposit,  followed  by 
rinsing  the  shavings  in  water. 

Trouble  is  often  experienced  in  precipitating  from  weak  solu- 
tions. It  is  impossible  to  predict  how  weak  a  cyanide  solution 
can  be  successfully  precipitated,  for  mill  solutions  showing  no 
free  cyanide  have  been  precipitated  to  a  trace  of  gold  and  silver. 
Solutions  weak  in  cyanide  precipitate  better  when  carrying  con- 
siderable protective  alkalinity  and  the  cyanogen  compounds 
that  accumulate  in  a  solution  when  working  a  clean  ore.  But 
such  solutions  precipitate  poorly  when  without  or  low  in  pro- 
tective alkali  or  when  fouled  through  the  large  accumulation  of 
the  compounds  that  enter  a  solution  when  treating  an  acid  or 
base  ore.  The  cause  and  remedying  of  poor  precipitation  from 
weak  solutions,  and  without  increasing  the  strength  of  solution, 
is  in  some  cases  a  difficult  problem  to  solve.  The  effectiveness 
of  the  precipitation  is  mainly  a  matter  of  keeping  the  zinc  clean 
and  free  from  everything  except  metallic  zinc  and  the  metals 
precipitated.  More  especially  in  keeping  the  zinc  free  from  the 
zinc  oxide,  hydroxide,  and  cyanide  insoluble  in  water  and  poorly 
soluble  in  weak  solution,  and  which  tend  to  form  by  contact  of 
zinc  and  water  or  weak  solution.  An  alkali  will  be  efficient  in 
doing  this,  just  as  cyanide,  by  promoting  a  vigorous  chemical 
action  which  dissolves  and  removes  the  fouling  compounds, 
which  dissolves  the  zinc  for  replacing  the  precious  metals,  arid 
which  sets  up  the  electric  currents  to  deposit  or  further  assist 
in  the  deposition  of  the  gold  and  silver. 

White  Precipitate.  —  One  cause  of  poor  precipitation  has  been 
the  formation  of  a  white  precipitate  in  the  zinc  boxes.  In  a  few 
cases  this  precipitate  has  been  lime  salts,  due  to  the  excessive 


PRECIPITATION  169 

use  of  lime  or  other  alkaline  neutralizer,  but  it  is  generally  zinc 
as  a  hydrate  (Zn(OH)2),  a  cyanide  (Zn(CN)2),  or  a  zinc  potas- 
sium ferrocyanide  (K2Zn3(Fe(CN)6)2),  with  some  salts  of  the 
bases.  This  precipitate  is  an  inert,  grayish-white,  and  some- 
what granular  substance  which  usually  forms  in  the  weak-solu- 
tion zinc  boxes  or  when  very  dilute  solution  is  being  run  through 
a  box.  It  also  forms  more  rapidly  when  treating  pyritic  ores  or 
those  containing  considerable  acidity,  especially  when  there  is 
no  protective  alkalinity  in  the  solution.  It  forms  in  the  upper 
compartments  of  the  boxes  and  greatly  hinders  precipitation 
by  coating  the  zinc  and  matting  and  caking  it  together.  A 
consideration  of  the  equations  shown  before  in  this  chapter  and 
what  has  been  said  under  Alkalinity  and  Lime  regarding  the 
reactions  in  the  zinc  boxes  show  that  the  white  precipitate  is 
due  to  too  low  a  strength  in  cyanide  and  alkalinity  of  the 
solution  passing  through  the  box.  When  solutions  are  low  in 
cyanide  and  alkalinity  the  zinc  potassium  cyanide,  which  may 
be  considered  to  normally  exist,  tends  to  disassociate  with  the 
formation  of  zinc  cyanide,  while  considerable  zinc  hydroxide 
forms  from  the  action  of  the  weak  solution  on  the  zinc.  Zinc 
cyanide  and  zinc  hydroxide  are  insoluble  in  water  and  naturally 
precipitate  in  weak  solutions,  but  are  soluble  in  solutions  of 
some  strength  in  cyanide  and  alkali.  Consequently  the  solu- 
tion should  be  kept  up  to  a  sufficient  strength  in  cyanide  and 
alkali  to  prevent  the  white  precipitate  from  forming,  or  if  formed 
a  strong  cyanide  solution  which  may  have  considerable  alka- 
linity should  be  run  through  the  boxes  to  dissolve  and  carry  out 
the  precipitate,  which  will  take  some  time.  In  some  cases  the 
zinc  has  been  taken  out  of  the  boxes  and  washed  in  strong 
caustic  soda  solution,  but  this  course  is  inadvisable,  as  increasing 
the  cyanide  strength  and  alkalinity  will  generally  remedy  the 
trouble,  except  where  the  zinc  and  zinc  slime  are  caked  with  a 
large  amount  of  the  white  precipitate,  which  may  necessitate 
disintegrating  the  cakes  and  lumps  by  a  species  of  clean-up. 
The  zinc  potassium  ferrocyanide,  which  probably  forms  to  a 
greater  extent  in  the  working  of  decomposed  pyritic  ores,  is 
less  soluble  in  alkaline  solutions  than  the  zinc  hydrate  and  zinc 
cyanide,  and  when  once  formed  may  require  a  clean-up  to 
remove.  For  the  purpose  of  keeping  the  boxes  clean  and  active 
and  the  quantity  of  white  precipitate  small,  the  solution  flows 


170  TEXT  BOOK  OF  CYANIDE  PRACTICE 

entering  the  strong  and  weak-solution  boxes  may  be  made  in- 
terchangeable, the  flows  to  be  alternated  as  may  be  necessary; 
or  no  division  is  made  in  the  solution  to  create  one  of  high  and 
another  of  low  strength,  but  all  is  kept  at  a  strength  that  will 
give  good  precipitation.  The  strength  of  weak  solution  is  some- 
times increased  by  a  drip  of  strong  solution  into  the  head  of 
the  box,  or  occasionally  adding  a  chunk  of  solid  cyanide  there, 
or  by  standardizing  or  adding  cyanide  or  lime  or  caustic  soda 
to  the  contents  of  the  gold  tank. 

Zinc-Lead  Couple.  --  The  zinc-lead  couple  has  been  used  to 
a  large  extent  to  secure  satisfactory  precipitation  from  weak 
solutions.  It  is  prepared  by  dipping  the  new  shavings  into  a 
5  to  10  per  cent  solution  of  lead  acetate  (Pb(C2H3O2)2.3  H2O) 
for  a  few  minutes  until  they  turn  black  from  the  lead  deposited, 
when  they  are  placed  in  the  compartments  as  usual.  In  some 
cases  a  1  per  cent  solution  of  lead  acetate  has  been  allowed  to 
drip  into  the  head  of  the  boxes,  though  dipping  appears  to  be 
the  better.  The  zinc  and  lead  together  form  a  galvanic  couple 
which  greatly  assists  precipitation. 

Copper  in  Solution.  —  Copper  in  solution  tends  to  precipitate 
when  the  solution  is  low  in  cyanide,  and  to  remain  in  solution 
when  the  cyanide  strength  is  high  and  interfere  with  the  disso- 
lution and  precipitation  of  the  precious  metals.  Small  quanti- 
ties of  copper  in  weak  solutions  are  precipitated  upon  the  bright 
new  zinc  in  the  lower  compartments.  When  the  amount  of 
copper  is  small,  this  does  not  interfere  with  the  precipitation, 
in  fact  it  usually  assists  through  the  formation  of  a  galvanic 
couple,  but  large  quantities  may  interfere  by  giving  the  zinc 
too  thorough  a  coating  of  copper  or,  when  remaining  in  solution, 
may  prevent  precipitation  of  the  gold  and  silver.  The  principal 
means  of  removing  the  copper  have  been  the  use  of  lead  shav- 
ings in  the  head  compartments  or  the  zinc  shavings  dipped  in 
lead  acetate  and  placed  in  the  lower  compartments,  lead  or  the 
zinc-lead  couple  being  a  good  precipitant  of  copper.  Attempts 
have  been  made  to  keep  the  amount  of  copper  dissolved  from 
the  ore  low  by  the  use  of  weak  dissolving  solutions,  and  then  to 
keep  the  copper  in  solution  by  raising  the  strength  of  the  solu- 
tion before  entering  the  zinc  boxes,  but  the  best  method  appears 
to  be  to  precipitate  the  copper  from  the  solution  in  some  con- 
venient way  and  get  it  out  of  the  system. 


PRECIPITATION  171 

Mercury  in  Solution.  —  Mercury  found  in  old  tailing  from 
amalgamation  mills  is  usually  changed  to  an  oxide,  salt,  or 
other  compound  which  is  readily  attacked  by  cyanide  solution. 
Mercury  in  its  metallic  state  is  slowly  dissolved  by  cyanide 
solution,  the  dissolved  metal  in  any  case  being  precipitated  in 
the  zinc  boxes  if  not  before.  A  small  amount  of  mercury  dis- 
solved in  this  manner  is  not  harmful  but  very  beneficial,  for  it 
is  the  best  substance  for  removing  alkaline  sulphides  by  form- 
ing an  insoluble  mercuric  sulphide  (HgS)  with  the  sulphur. 
Compounds  of  mercury,  principally  mercuric  chloride,  have 
sometimes  been  used  for  this  purpose  with  excellent  results. 
Small  quantities  of  mercury  on  the  shavings  may  increase  pre- 
cipitation through  the  formation  of  a  mercury-zinc  galvanic 
couple,  but  large  quantities  are  detrimental  through  causing 
the  shavings  to  break  up  and  slime.  Where  the  zinc  slime 
contains  a  large  amount  of  mercury,  it  may  be  retorted  to  secure 
the  mercury  before  being  treated  for  its  gold  and  silver. 

Cutting  of  Zinc  Shavings.  —  Care  must  be  exercised  in  cut- 
ting zinc  shavings  or  in  purchasing  shavings  already  cut,  as  zinc 
oxidizes  easily  when  heated.  With  careless  cutting  the  zinc 
heats  rapidly  and  is  often  further  assisted  to  oxidize  through 
being  cooled  by  cold  water  poured  over  it.  Such  partly-oxi- 
dized zinc  is  not  highly  efficient  in  precipitating  and  unduly 
breaks  into  short  zinc.  Zinc  exposed  to  the  atmosphere  slowly 
oxidizes,  consequently  fresh-cut  zinc  is  the  best.  •  Zinc  contain- 
ing a  small  amount  of  lead  is  an  excellent  precipitant  as  it  is  a 
zinc-lead  galvanic  couple  without  further  treatment;  in  fact, 
most  zinc  shavings  contain  a  small  amount  of  impurities  which 
are  beneficial,  and  zinc  dust  containing  a  small  percentage  of 
lead  is  sometimes  ordered. 

Mechanical  and  Chemical  Consumption  of  Zinc.  —  Zinc  is 
consumed  in  the  precipitating  process  in  two  ways  —  chemically 
and  mechanically.  The  zinc  chemically  consumed  by  the  reac- 
tions in  the  zinc  boxes  goes  out  of  the  plant  in  the  solution  dis- 
charged with  the  tailing  residue  and  lost  by  leakage,  by  being 
precipitated  in  the  zinc  boxes  as  spoken  of  in  connection  with 
the  white  precipitate,  and  mainly  by  being  precipitated  in  the 
ore.  The  nature  of  the  precipitation  occurring  in  the  ore  is  not 
well  known,  but  is  supposed  to  be  with  alkaline  sulphides  to 
form  the  insoluble  zinc  sulphide,  to  be  precipitated  as  a  zinc 


172  TEXT  BOOK  OF  CYANIDE  PRACTICE 

carbonate,  or  the  precipitation  may  take  place  in  the  ore  under 
conditions  similar  to  those  by  which  the  white  precipitate  is 
formed  in  the  zinc  boxes.  It  is  an  interesting  fact  that  the 
amount  of  zinc  in  a  plant  solution  remains  fairly  constant 
though  the  solution  be  used  for  years.  The  zinc  in  solution  is 
generally  considered  to  exist  as  a  zinc  potassium  cyanide 
(K2Zn(CN)4),  more  especially  when  the  difference  between  the 
free  and  total  cyanide  indicates  enough  cyanogen  to  be  com- 
bined with  the  zinc,  which  by  the  formula  would  be  1  pound 
cyanogen  in  terms  of  potassium  cyanide  combined  with  .251 
pound  of  zinc.  It  has  been  observed  that  as  the  zinc  potassium 
cyanide  is  apparently  regenerated  into  free  cyanide,  by  increasing 
the  protective  alkalinity  or  as  the  free  and  total  cyanide  ap- 
proach each  other,  the  amount  of  zinc  in  solution  falls,  but 
exactly  how  it  is  removed  under  these  conditions  is  unknown. 

The  zinc  consumed  mechanically  in  the  precipitating  process 
is  that  removed  from  the  boxes  with  the  gold-silver  slime  to  be 
treated  and  melted  into  bullion.  The  amount  of  zinc  con- 
sumed in  this  way  is  high  in  a  gold  plant,  since  much  short  zinc 
is  removed  from  the  boxes  to  be  acid  treated,  etc.,  in  the  effort 
to  get  all  the  bullion  possible.  In  a  silver  plant  the  amount  is 
much  less  since  a  close  clean-up,  as  referring  to  the  comparative 
weight  of  precious  metal  left  in  the  boxes,  is  not  made.  The 
stronger  the  solution  used,  the  greater  will  be  the  chemical 
consumption.  •  The  weaker  the  solution,  the  greater  will  be  the 
mechanical  loss,  for  the  use  of  weak  solutions  is  attended  with 
the  production  of  much  short  zinc  and  other  zinc-box  troubles, 
especially  when  the  solution  is  also  low  in  gold  and  silver.  The 
precipitation  of  rich  solutions  is  attended  with  a  much  less  con- 
sumption of  zinc  mechanically  and  often  chemically  than  that 
of  low-grade  solutions. 

The  consumption  of  zinc  is  usually  reported  on  the  basis  of 
the  tons  of  ore  treated.  For  technical  purposes  it  is  also  de- 
sirable to  report  it  on  the  basis  of  tons  of  solution  precipitated 
and  ounces  of  bullion  produced,  for  ores  require  widely  varying 
amounts  of  solution  for  their  treatment;  likewise  the  value  of 
ores  and  the  richness  of  their  solutions  vary.  The  amount  of 
zinc  shavings  used  will  vary  from  J  to  J  pound  per  ton  of  ore 
treated  in  a  gold  plant,  and  in  a  silver  plant  from  f  to  1|  pounds 
and  upward.  The  consumption  will  vary  from  J  to  J  pound  per 


PRECIPITATION  173 

ton  of  solution  precipitated.  On  a  gold  plant  the  consumption 
will  be  from  4  to  20  parts  of  -zinc  to  1  part  of  bullion  produced, 
while  in  a  silver  plant  1J  parts  and  upward  will  produce  1  part 
of  bullion.  Theoretically,  in  the  replacement  by  zinc  of  the 
gold  and  silver  in  the  potassium  gold  or  silver  cyanide  (KAu(CN)2 
or  KAg(CN)o)  formed  in  the  dissolving  process,  1  part  of  zinc 
should  precipitate  3  parts  of  gold  or  1.65  parts  of  silver. 

Regeneration  of  Cyanide  and  Alkalinity.  —  There  is  often  an 
apparent  regeneration  of  free  cyanide  taking  place  in  the  zinc 
box  as  shown  by  titrating  the  solution  entering  and  leaving 
the  box.  This  may  amount  to  as  much  as  J  or  \  pound  per 
ton  of  solution.  The  exact  cause  of  the  regeneration  is  inde- 
terminate, but  is  due  to  the  complex  reactions  occurring  in 
the  zinc  box.  There  is  also  a  slight  increase  in  the  alkalinity; 
this  can  be  more  clearly  understood  than  the  regeneration  of 
cyanide,  by  considering  the  equation  representing  the  pre- 
cipitating reaction  which  indicates  the  formation  of  caustic 
potash  or  a  similar  alkali. 

Zinc-Dust  Precipitation.  —  Zinc  dust  is  a  highly  satisfactory 
precipitant  of  gold  and  silver,  due  to  its  fine  state  of  division, 
its  agitation  with  the  solution,  and  the  forcing  of  the  solution 
through  that  already  in  use.  As  at  first  developed  the  solu- 
tion to  be  precipitated  was  run  into  tanks  holding  from  15  tons 
upward  of  solution.  After  a  tank  was  filled  with  solution  it 
was  agitated,  usually  by  air  pipes  in  the  bottom  of  the  tank. 
Fresh  zinc  dust  amounting  to  about  J  to  J  pound  per  ton  of 
solution  was  sprinkled  over  the  charge.  This  zinc  dust  together 
with  that  already  in  the  tank  from  previous  charges  and  stirred 
up  by  the  agitation  was  sufficient  to  precipitate  the  metal  with 
15  minutes  or  more  agitation,  after  which  the  solution  was 
drained  through  plate  and  frame  filter  presses  to  the  barren 
sump  tanks.  In  the  filter  press  the  solution  passed  through 
the  already-acted-upon  zinc  which  gradually  accumulated  by 
being  carried  in  from  the  agitation  tanks. 

As  at  present  used  the  zinc  dust  is  fed  continuously  to  the 
solution  by  being  spread  upon  a  long,  slow-moving  belt  or  by 
other  feeding  device  —  due  to  the  small  quantity  of  dust  con- 
stantly required  and  its  tendency  to  agglomerate,  it  has  been 
hard  to  secure  a  satisfactory  automatic  feeding  mechanism. 
The  dust  is  usually  fed  together  with  the  solution  into  a  mixing 


174 


TEXT  BOOK  OF  CYANIDE  PRACTICE 


and  agitating  device  wherein  the  precious  metal  is  largely  pre- 
cipitated. The  solution  then  runs  to  or  is  pumped  through 
the  precipitation  plate  and  frame  filter  press.  Or  the  zinc  dust 
is  fed  to  the  solution  at  the  intake  of  the  pipe  leading  to  the 
press.  The  press  is  located  as  far  from  the  intake  or  mixing 
device  as  possible,  to  secure  the  better  precipitating  effect  of 
moving  solution  and  zinc  dust.  No  air  is  allowed  to  reach  the 
press  as  would  be  the  case  were  it  or  the  intake  drained,  or  the 


Fig.  32.  —  Merrill  Precipitation  Press. 

zinc  will  become  much  oxidized.  The  precipitated  metal  or  zinc- 
gold  slime  is  removed  by  opening  the  press  and  separating  the 
frames,  allowing  the  slime  to  fall  into  pans  underneath.  The 
filter  cloths  are  scraped  clean  and  returned,  or  are  occasionally 
burned  and  added  to  the  meltings.  An  increased  quantity  of 
zinc  dust  is  used  when  starting  anew  after  a  clean-up  —  at  which 
time  any  zinc  slime  in  the  agitation  tanks  or  mixing  device  is 
removed  —  until  a  quantity  has  accumulated  in  the  press. 
The  amount  of  dust  used  is  increased  or  decreased  as  the  tailing 
solution  increases  or  decreases  in  the  amount  of  gold  and  silver 
still  unprecipitated.  Zinc  dust  is  especially  efficacious  in  pre- 
cipitating from  weak  and  low-grade  solutions.  In  these  cases 
it  is  often  assisted  by  the  zinc-lead  couple  formed  through 


PRECIPITATION  175 

allowing  a  solution  of  lead  acetate  to  drip  into  the  mixing  device 
or  using  dust  containing  a  little  lead.  The  amount  of  zinc 
dust  used  is  about  equal  to  the  shavings  that  would  be  required; 
in  some  cases  more  is  necessary,  but  with  careful  manipulation 
less  can  be  employed.  The  cost  of  dust  is  about  one-third  less 
than  of  shavings.  The  fineness  of  the  precipitate  in  gold  and 
silver,  or  the  proportion  of  the  precious  metals  to  the  base  metals 
or  zinc,  is  about  that  of  slime  from  zinc  shavings  washed  through 
a  30-mesh  screen,  and  is  subject  to  being  increased  by  careful 
manipulation,  principally  through  the  cyanide  dissolving  more 
of  the  zinc  collecting  in  the  press  and  thus  reducing  the  zinc 
content  of  the  precipitate.  One  of  the  advantages  of  using 
zinc  dust  is  that  the  entire  metal  precipitated  is  obtained  each 
clean-up,  and  none  is  left  remaining  as  in  the  case  of  using  zinc 
shavings.  This  indicates  that  the  zinc-dust  process  is  more 
applicable  for  gold  than  for  silver  plants,  since  in  a  gold  plant 
much  of  the  short  zinc  is  collected  into  the  clean-up  and  con- 
siderable value  left  in  the  box,  whereas  in  a  silver  plant  only 
the  fine,  slimy  precipitate  is  taken,  making  the  cost  of  refining 
and  the  mechanical  consumption  of  zinc  less,  while  less  value 
is  left  in  the  box.  The  zinc-dust  process  is  more  adapted  to 
large  than  to  small  plants,  since  the  installation  cost  is  high 
and  it  requires  more  continuous  attention  than  the  zinc-shaving 
method.  The  installation  and  labor  costs  are  not  in  proportion 
to  the  tonnage,  but  fall  rapidly  per  ton  treated  as  the  plant  is 
increased  in  size.  The  installation  and  working  out  of  a  success- 
ful zinc-dust  precipitation  method  requires  higher  ability  and 
closer  study  than  with  shaving  precipitation,  but  is  capable  of 
being  developed  to  a  higher  degree  of  efficiency  and  economy. 


CHAPTER  XIII 
CLEANING-UP 

THE  precipitated  gold  and  silver  are  removed  from  the  zinc 
boxes  or  presses  usually  weekly  or  semi-monthly  in  a  silver 
plant,  and  semi-monthly  or  monthly  in  a  gold  plant  It  is 
customary  to  run  a  strong  cyanide  solution  —  .75  per  cent 
(15  pounds)  to  1  per  cent  (20  pounds)  —  through  the  boxes  for 
a  few  hours  before  the  clean-up  is  started,  to  loosen  the  gold- 
silver  slime  deposited  on  the  zinc;  it  also  cleans  some  of  the 
dissolvable  white  precipitate  out  of  the  boxes.  The  cyanide 
solution  is  displaced  by  running  water  through  the  boxes  for 
an  hour  or  longer,  that  the  cyanide  may  not  injure  the  hands, 
tend  to  redissolve  the  gold,  or  appear  in  the  cleaned-up  pre- 
cipitate. The  operator  lifts  the  zinc  from  the  first  compart- 
ment into  a  tub,  preferably  filled  with  water  to  prevent  the 
zinc  from  oxidizing  through  exposure  to  the  air.  All  the  zinc 
is  removed  from  the  compartment,  also  the  screen  in  the  bottom. 
A  screen  is  now  suspended  in  the  compartment  and  the  removed 
zinc  washed  on  it  as  free  from  slime  as  possible,  by  being  dis- 
entangled, gently  teased,  rinsed,  and  finally  being  rinsed  in  a 
clearer  water.  Care  is  taken  to  break  the  zinc  up  as  little  as 
possible  into  short  zinc.  Three  products  are  made  in  the  proc- 
ess of  washing :  the  slime  passing  through  the  screen,  the  washed 
"  shorts  "  or  "  met  allies  "  not  passing  through  the  screen  and 
up  to  two  or  three  inches  in  length,  and  the  washed  long  zinc. 

After  all  the  zinc  taken  from  the  first  compartment  is  washed, 
the  drain  plug  at  the  bottom  of  the  compartment  is  opened  to 
allow  the  water  and  the  gold-silver  slime,  including  that  just 
washed  free  from  the  zinc  and  that  which  had  previously  fallen 
through  the  screen,  to  run  through  a  launder  or  hose  into  a 
sludge  or  precipitate  tank.  The  compartment  is  washed  out 
with  a  little  clean  water,  and  the  plug  and  screen  replaced. 
If  there  is  no  bottom  discharge  and  drain  launder  or  hose,  the 
contents  of  the  compartment  may  be  allowed  to  settle,  the 

176 


CLEANING-UP  177 

water  syphoned  off,  and  the  slime  dipped  out  and  carried  in 
pails  to  the  sludge  or  clean-up  tank.  Having  replaced  the 
screen,  a  two  or  three-inch  layer  of  new  zinc,  preferably  cut 
coarser  than  regularly,  is  placed  evenly  over  the  screen;  on 
this  is  spread  a  two-inch  layer  of  the  washed  short  zinc,  then  a 
layer  of  the  washed  long  zinc,  followed  by  short  zinc,  and  so 
on  until  full,  as  described  in  connection  with  the  care  of  zinc 
boxes.  The  zinc  is  kept  under  water  as  much  as  possible  at 
all  times  to  prevent  oxidation.  The  second  and  succeeding 
compartments  are  treated  similarly,  though  in  most  cases  where 
the  zinc  has  been  moved  toward  the  head  of  the  box,  not  more 
than  the  first  three  compartments  need  be  cleaned  out,  for  in 
the  others  an  appreciable  amount  of  slime  cannot  be  secured. 
In  some  cases  the  zinc  is  transferred  to  a  clean-up  tank,  there 
to  be  washed  and  returned  to  the  compartments. 

The  slime  flowing  from  the  compartments  is  washed  through 
a  screen  into  the  sludge  or  clean-up  tank.  The  mesh  of  this 
screen  and  that  used  in  washing  the  zinc  in  the  boxes  will  vary 
with  how  close  a  clean-up  is  desired,  or  how  much  short  zinc 
is  to  be  included  in  the  clean-up.  In  a  gold  plant  all  zinc  not 
washed  through  a  10  or  20-mesh  screen  is  usually  returned  to 
the  boxes,  in  some  cases  still  coarser  zinc  is  put  into  the  clean- 
up, though  the  amount  of  precious  metal  in  the  short  zinc  is 
comparatively  very  small.  In  a  silver  plant,  owing  to  the 
lesser  value  of  the  same  weight  of  silver  bullion  as  of  gold  bullion, 
only  the  slime  passing  through  a  30  to  60-mesh  screen  is  generally 
taken,  all  the  short  zinc  being  returned  to  the  box.  This  results 
in  a  precipitate  high  in  bullion,  usually  60  to  75  per  cent,  and 
low  in  zinc.  When  the  quantity  of  short  zinc  is  too  large  to 
be  advantageously  placed  with  the  long  zinc,  it  may  be  put  in 
trays  suspended  in  the  head  compartment,  or  provisions  made 
for  agitating  it  with  rich  solution  to  precipitate  the  gold  and 
silver  in  a  way  similar  to  zinc  dust,  being  used  in  this  manner 
until  cut  or  dissolved  to  a  slime.  It  may  be  advisable  to  screen 
the  precipitate  to  be  refined  into  two  classes,  that  held  on  a 
30  to  60-mesh  screen,  high  in  zinc  and  low  in  bullion,  and  that 
passing  the  screen,  which  would  be  high  in  bullion  and  low  in 
zinc,  so  that  separate  treatment  may  be  given  each. 

If  the  precipitate  is  not  to  be  acid  treated  it  is  pumped  into 
a  small  plate  and  frame  filter  press,  where  it  may  be  dried  by 


178  TEXT  BOOK  OF  CYANIDE  PRACTICE 

blowing  air  through  before  the  frame  is  opened  for  the  removal 
of  the  precipitate.  Or  the  precipitate  may  be  run  into  a  small 
tank  with  a  false  bottom  similar  to  that  of  a  leaching  vat,  the 
moisture  being  drawn  off  and  the  precipitate  partially  dried  by 
producing  a  vacuum  underneath  the  filter  cloth.  In  either  case 
the  water  drawn  from  the  precipitate  is  pumped  to  the  head 
of  the  zinc  boxes  to  catch  any  fine  precipitate,  or  run  into  a 
tank  where  it  is  settled  and  later  used  as  plant  solution,  the 
settlings  going  into  a  clean-up. 


CHAPTER  XIV 

ROASTING   AND   ACID   TREATMENT 

THE  precipitate  may  be  refined  into  bullion  in  four  ways: 

Melting. 

Roasting  and  melting. 

Acid  treatment  and  melting,  with  or  without  roasting. 

Smelting  with  litharge  and  cupellation. 

In  melting  the  precipitate  without  further  treatment,  it 
may  be  completely  dried  in  a  pan  set  in  an  oven  or  over  a  fire 
or  in  a  steam-jacketed  pan.  Or  it  may  be  dried  as  well  as 
possible  while  in  the  plate  and  frame  precipitation  or  clean-up 
press  or  in  the  clean-up  vacuum  tank,  by  blowing  or  drawing 
air  through,  followed  by  mixing  with  flux  and  melting  without 
further  drying.  Melting  without  further  treatment  is  advisable 
with  a  precipitate  high  in  gold  and  silver  and  low  in  zinc,  such 
precipitate  as  would  pass  a  40  to  60-mesh  screen.  As  the 
quantity  of  metallic  zinc  in  the  precipitate  increases,  the  fine- 
ness of  the  bullion  will  decrease  and  more  zinc  will  go  into  the 
bar.  Also  more  gold  and  silver  will  be  carried  off  mechanically 
in  a  finely-divided  state  by  the  dense  fumes  arising  from  the 
volatilization  of  the  zinc. 

Roasting.  —  Roasting  the  precipitate  before  melting  con- 
verts the  zinc  into  an  oxide,  so  that  it  can  much  more  easily 
enter  into  the  slag  as  a  silicate  of  zinc  or  dissolved  metallic 
oxide,  instead  of  into  the  bullion  as  much  of  it  does  when  it 
has  not  been  converted  into  the  oxide.  Other  base  metals  and 
substances  are  more  or  less  oxidized,  decomposed,  or  volatilized 
to  render  the  subsequent  melting  and  the  slagging  off  of  the 
foreign  substances  easier  and  the  grade  of  the  bullion  higher. 
Roasting  is  especially  advisable  with  the  coarser  precipitate 
which  must  contain  much  zinc,  as  a  high-grade  bullion  with 
but  little  zinc  and  bases  can  be  secured  in  this  way  from  such 
material.  The  precipitate  to  be  roasted  is  placed  in  heavy 

179 


180  TEXT  BOOK  OF  CYANIDE  PRACTICE 

cast-iron  pans  which  are  put  into  ovens  or  roasting  furnaces; 
they  are  even  put  over  fireplaces  and  a  fire  built  directly  under 
them.  It  is  hard  to  say  to  what  extent  the  roasting  should  be 
carried.  The  better  the  roasting,  the  better  the  zinc  and  bases 
will  be  oxidized  to  pass  into  the  slag.  The  roasting  is  often 
carried  to  the  point  where  the  zinc  takes  a  dull  fire.  This  is 
not  harmful  if  the  roasting  has  been  carried  on  slowly  so  .that 
the  fumes  and  ebullition  do  not  carry  off  gold  and  silver,  so 
that  the  zinc  oxidizes  instead  of  volatilizes.  Niter,  potassium 
nitrate  (KNO3),  to  the  amount  of  3  to  10  per  cent  is  sometimes 
well  mixed  with  the  precipitate  before  roasting,  either  as  a 
powder  or  as  a  solution  saturating  the  precipitate.  This  causes 
a  rapid  and  complete  oxidation  by  converting  the  zinc  into 
zinc  oxide,  which  being  nonvolatile,  does  not  carry  finely- 
divided  gold  and  silver  away  in  the  fumes.  The  farther  the 
roasting  is  carried,  the  higher  the  loss  will  be,  though  the  use 
of  condensing  chambers  has  shown  that  the  loss  is  small.  During 
the  roasting  process  the  slime  should  be  stirred  as  little  as  pos- 
sible or  not  at  all  to  avoid  loss  by  dusting. 

Acid  Treatment.  —  In  the  acid  treatment  the  precipitate  is 
settled  and  dewatered  by  decantation  in  the  sludge  tank  into 
which  it  runs  from  the  zinc  boxes,  and  acid  added  to  dissolve 
the  zinc.  The  acids  used  are  sulphuric  (H2SO4),  sulphurous 
(H2SO3),  hydrochloric  (HC1),  and  bisulphate  of  sodium  (NaHSO4). 
Nitric  acid  (HNO3)  has  also  been  used,  but  its  use  is  inadvisable 
as  it  dissolves  more  of  the  precious  metals  than  the  other  acids. 
Hydrochloric  acid  has  been  used  to  a  slight  extent.  It  has  a 
greater  cost  and  a  higher  dissolving  effect  on  the  precious  metals, 
but  has  the  advantage  of  forming  soluble  chlorides  with  the 
lime  and  lead  that  may  be  removed  by  washing.  Acid  treat- 
ment is  generally  not  attempted  with  silver  precipitate,  since 
the  short  zinc  is  usually  returned  to  the  boxes  leaving  a  slime 
high  in  bullion,  while  the  acid  tends  to  dissolve  silver  and  thereby 
cause  a  loss.  Gold  precipitate  is  usually  acid  treated,  especially 
if  it  contains  much  short  zinc,  either  treating  all  the  precipitate 
or  only  that  going  into  the  clean-up  which  does  not  pass  a  40 
to  60-mesh.  It  is  seldom  profitable  to  treat  the  gold  slime 
passing  a  40-mesh  by  acid,  except  when  it  is  desired  to  treat 
coarser  material  and  the  facilities  do  not  allow  of  a  segregation 
of  the  two  classes  of  material. 


ROASTING  AND  ACID  TREATMENT  181 

Sulphuric  Acid  Treatment.  —  Sulphuric  acid  (H2SO4)  is  gen- 
erally used  for  dissolving  out  the  zinc  and  to  some  extent  the 
other  bases  before  melting,  forming  zinc  sulphate  (ZnSO4)  and 
other  sulphates.  After  the  water  has  been  decanted  off  the 
settled  slime  in  the  sludge  or  clean-up  tank,  which,  if  acid  treat- 
ment is  to  be  carried  out,  should  be  of  wood  or  lead  lined,  the 
sulphuric  acid  is  slowly  and  carefully  added  to  avoid  the  charge 
boiling  over,  in  an  amount  making  from  a  10  to  20  per  cent 
solution  of  sulphuric  acid.  Theoretically  one  part  of  zinc 
requires  1J  parts  of  sulphuric  acid  to  be  converted  into  zinc 
sulphate,  while  a  16  per  cent  solution  of  sulphuric  acid  appears 
to  act  to  the  best  advantage  on  zinc.  In  actual  practice  from 
f  to  1J  pounds  of  cheap  commercial  sulphuric  acid  is  used  for 
each  pound  of  dry  precipitate,  the  amount  of  dry  precipitate 
and  its  moisture  being  estimated  and  the  sulphuric  acid  and  any 
additional  water  being  first  added  by  this  estimation,  sulphuric 
acid  being  finally  added  according  to  the  continuance  of  the 
reaction.  On  the  addition  of  the  acid,  there  is  an  active  libera- 
tion and  forcible  ebullition  of  hydrogen  as  vile- smelling  fumes, 
also  some  hydrocyanic  acid  from  the  decomposition  of  cyanogen 
compounds  in  the  precipitate,  for  which  reason  the  refining 
tank  is  covered  with  a  hood  and  uptake  to  carry  off  the  fumes. 
As  soon  as  it  is  seen  that  the  boiling  has  subsided  to  a  point 
where  the  sludge  may  be  stirred  without  danger  of  boiling  over, 
stirring  is  carried  on  mechanically  or  by  hand.  A  sudden 
tendency  to  boil  over  is  stopped  by  the  addition  of  cold  water. 
The  heat  developed  by  mixing  the  acid  and  water  and  the  chem- 
ical reactions  is  sufficient  to  cause  the  active  formation  of  zinc 
and  other  sulphates.  Sulphuric  acid  is  added  from  time  to 
time  with  thorough  stirrings  until  there  is  no  more  reaction, 
showing  that  the  zinc  has  been  dissolved  and  that  the  acid  is  in 
excess  of  that  required.  Stirring  should  be  continued  for  half 
an  hour  after  all  action  has  ceased.  The  "  cutting  down  "  of 
the  precipitate  by  acid  may  be  accomplished  within  a  few  hours, 
but  usually  an  entire  shift  is  allotted  to  it.  The  operator  must 
use  care  not  to  be  overcome  by  the  fumes.  Breathing  the  fumes 
of  ammonia  affords  relief.  Where  the  ore  contains  arsenic, 
fumes  of  arseniureted  hydrogen  may  be  given  off  which  are 
highly  poisonous;  several  deaths  have  occurred  from  this.  Pre- 
liminary treatment  with  nitric  acid  or  a  general  treatment  with 


182          TEXT   BOOK  OF  CYANIDE  PRACTICE 

one  part  nitric  and  two  parts  sulphuric  acid  to  change  the  arsenic 
into  a  nonvolatile  arsenic  acid  has  been  recommended  or  treat- 
ment made  with  bisulphate  of  sodium,  though  it  would  appear 
better  to  dispense  with  acid  treatment  on  such  precipitate.  - 

The  tank  is  filled  with  water  and  thoroughly  stirred  after  the 
zinc  has  been  cut  down  by  the  acid,  after  which  the  precipitate 
is  allowed  to  settle  and  the  acid  and  sulphate  solution  decanted 
off.  Three  or  four  or  more  washes  by  decantation  may  be  given 
in  this  way  with  water,  when  the  sludge  is  allowed  to  run  or  is 
pumped  into  a  small  plate  and  frame  filter  press  or  a  vacuum 
filter  tank  as  used  in  the  clean-up  process,  where  it  is  washed 
free  from  all  sulphates  and  soluble  matter  by  pumping  or  draw- 
ing water  through.  The  washing  by  decantation  and  in  the 
press  or  tank  is  usually  with  cold  water,  though  there  is  some 
advantage  in  using  hot  water  as  is  often  the  practice,  since  one 
part  of  water  at  1°  C.  will  dissolve  .42  part  zinc  sulphate,  at 
20  degrees  will  dissolve  .53  part,  at  50  degrees  will  dissolve  .67 
part,  and  at  75  degrees  will  dissolve  .80  part.  Lead  sulphate 
(PbS04)  is  practically  insoluble,  while  one  part  of  calcium  sul- 
phate (CaSO4)  is  soluble-  in  500  parts  of  water.  Whereas  the 
solubility  of  calcium  chloride  is  one  part  in  1J  of  water,  and  of 
lead  chloride  (PbCl)  is  one  part  in  93  parts  of  water.  Which 
indicates  the  advantage  of  using  hydrochloric  acid  when  the 
precipitate  contains  large  quantities  of  lime  or  lead.  The  lead 
and  calcium  sulphates  besides  entering  the  acid-treated  slime, 
may  coat  the  zinc  so  that  it  is  not  acted  upon.  A  thick,  solid 
deposit  of  gold  and  silver,  such  as  sometimes  takes  place  from 
an  extremely  rich  solution,  may  prevent  the  zinc  from  being 
acted  upon. 

The  acid  washes  should  be  collected  in  a  tank  and  allowed  to 
settle  until  the  next  clean-up,  when  they  are  syphoned  to  waste. 
Or  they  may  be  agitated  with  scrap  zinc  before  settling,  or  run 
to  waste  through  such  zinc. 

The  partly-dried  slime  is  removed  from  the  clean-up  press  or 
vacuum  tank  and  may,  if  containing  a  small  amount  of  moisture, 
be  fluxed  and  melted  without  further  drying;  it  may  be  dried 
before  fluxing  and  melting,  or  it  may  be  roasted  before  fluxing 
and  melting,  the  roasting  being  very  similar  to  that  given 
precipitate  that  has  not  been  acid  treated  and  may  include 
adding  a  small  amount  of  niter.  Acid  treatment  by  sulphuric 


ROASTING  AND  ACID  TREATMENT  183 

acid  followed  by  a  thorough  roasting  is  the  method  usually 
employed  in  America  on  gold>  slime,  while  silver  slime  with  or 
without  roasting  is  melted  without  acid  treatment. 

Sulphurous  Acid  Treatment.  —  Refining  by  sulphurous  acid 
(H2S03)  does  not  differ  materially  from  that  by  sulphuric  acid. 
Metallic  or  solid  sulphur  is  burned  in  a  simple  generator  or  air- 
tight stove  supplied  with  air  under  a  pressure  of  a  few  pounds, 
sufficient  to  give  the  necessary  oxygen  to  form  sulphur  dioxide 
(S02),  and  force  it  into  a  clean-up  tank  to  be  absorbed  by  the 
water  therein  with  the  formation  of  sulphurous  acid,  as : 

SO2  +  H2O  =  H2SO3. 

The  precipitate  may  be  added  before  or  after  the  water  has 
absorbed  sufficient  acid.  The  zinc  is  dissolved  as: 

Zn  +  H2SO3  =  ZnSO3  +  2  H. 

The  sulphites  of  lead  and  lime  formed  appear  to  be  more  soluble 
in  an  excess  of  the  acid  than  the  sulphates  formed  similarly  in 
the  sulphuric-acid  treatment,  but  are  not  soluble  in  water.  The 
method  seems  to  be  as  efficient  as  the  sulphuric-acid  treatment 
with  a  remarkably  low  cost,  while  the  solid  sulphur  is  much 
easier  transported  than  the  liquid  and  dangerous  sulphuric  acid. 
The  method  has  been  successfully  used  in  America. 

Bisulphate  of  Sodium  Treatment.  —  In  refining  or  cutting 
down  the  zinc  by  a  solution  of  bisulphate  of  sodium  (NaHSO4),  — 
which  occurs  as  a  solid  substance,  —  the  chemical  is  dissolved  in 
a  stock  tank  to  dilute  the  acid  solution  used  in  treating  the  zinc 
to  equal  about  10  per  cent  H2SO4.  The  dissolving  takes  place 
as  in  the  ordinary  sulphuric-acid  method,  but  it  is  claimed  with 
less  danger  from  gassing  or  from  poisoning  by  arseniureted  hydro- 
gen. The  reaction  being: 

2  NaHSO4  -f  Zn  =  NasSO,  +  ZnSO4  +  2  H. 

The  principal  advantage  of  using  bisulphate  of  sodium  is  that, 
occurring  as  a  solid  chemical,  it  may  be  easier  transported  than 
sulphuric  acid,  and  may  be  a  cheaper  method  of  refining.  It 
will  be  noticed  that  not  all  of  the  sulphur  is  made  available  to 
unite  with  the  zinc.  The  method  is  being  used  to  a  limited 
extent  in  South  Africa. 


CHAPTER  XV 

FLUXING  AND  MELTING 

Constituents  of  Zinc  Slime  to  be  Melted.  —  The  nature  of  the 
precipitate  to  be  smelted  varies  widely,  due  to  the  different 
conditions  under  which  the  precipitation  takes  place,  and  more 
so  as  to  the  methods  of  cleaning-up  and  preliminary  refining. 
This  relates  to  the  amount  in  the  precipitate  of  gold  and  silver, 
of  zinc,  of  other  base  metals  and  substances,  what  these  bases 
are,  and  in  what  form  they  exist,  whether  metallic  or  as  oxides, 
sulphates,  etc.  The  constituents  of  a  precipitate  may  be  divided 
into  four  classes: 

Gold  and  silver. 

Metals  and  bases  as  oxides  and  sulphates. 

Metals  in  their  metallic  form  and  other  reducers. 

Silica  or  lime. 

The  larger  the  amount  of  gold  and  silver,  the  less  will  be  the 
amount  of  flux  required,  for  the  bases  to  be  slagged  off  will  be 
less.  The  percentage  of  precious  metals  in  the  precipitate  is 
controlled  by  the  manner  in  which  the  precipitation  is  conducted 
and  the  fineness  of  the  screen  through  which  the  clean-up  is 
made.  The  percentage  in  the  precipitate  is  further  increased 
by  the  roasting  or  acid  treatment  which  removes  part  of  the 
bases.  The  bases  changed  to  sulphates  by  the  acid  treatment 
are  removed  by  washing,  except  those  sulphates  which  are 
insoluble  in  water  and  sulphuric  acid,  mainly,  calcium  sulphate 
and  lead  sulphate.  Imperfect  washing  may  cause  some  of  the 
soluble  sulphates  to  remain  in  the  precipitate.  The  oxides  are 
formed  in  the  roasting  process,  whether  without  or  following 
acid  treatment.  The  base  metals  in  their  metallic  form  are 
those  that  have  not  been  acted  upon  by  the  roasting  or  acid 
treatment,  or  are  to  be  found  wnen  no  such  treatment  has  been 
given  the  precipitate.  They  are  principally  zinc  and  also  lead 
where  the  zinc-lead  couple  has  been  used.  Other  reducers  are 
insoluble  cyanogen  compounds  that  have  been  precipitated  in 

184 


FLUXING  AND  MELTING  185 

the  zinc  boxes.  Silica  is  due  to  turbid  and  slimy  solutions 
passing  through  the  boxes,  or  to  a  deposition  of  dissolved  silica 
or  alumina  on  the  zinc.  Lime  and  other  alkaline  substances 
may  be  deposited  in  the  boxes  when  the  protective  alkalinity 
is  high,  and  not  be  removed  by  roasting  or  acid  treatment. 

Purpose  of  Fluxing  and  Smelting.  —  The  purpose  of  fluxing 
and  smelting  is  to  form  a  slag  containing  the  base  metals  and 
substances,  mainly  as  silicates,  borates,  and  dissolved  oxides, 
and  to  form  a  bar  of  fine  bullion  containing  the  gold  and  silver. 
To  form  these  two,  —  the  slag  and  the  bullion,  —  it  is  necessary  to 
add  flux  to  the  precipitate  that  will  unite  with  the  bases  in  the 
proper  proportion  to  give  a  slag  that  is  fluid,  so  that  the  small 
shots  and  particles  of  gold  and  silver  may  easily  settle  down 
into  the  bar  of  bullion,  instead  of  remaining  suspended  to  form 
a  rich  slag:  one  that  will  form  and  be  liquid  at  a  low  heat; 
that  will  be  neutral  and  not  so  basic  as  to  destroy  the  crucible 
through  abstracting  the  clay  in  its  demands  for  acid  or  siliceous 
flux  to  slag  with  the  bases  of  the  precipitate;  that  will  not  be 
so  acid  as  to  utilize  more  flux  than  can  be  economically  gotten 
along  with  and  require  a  high  heat  to  make  fluid  —  a  neutral 
slag  is  usually  more  liquid;  and  that  will  be  of  small  bulk  to 
fuse  the  largest  amount  of  precipitate  and  take  up  the  least 
melting  space. 

Sodium  and  Potassium  Carbonates  as  Fluxes.  —  As  fluxes 
used  in  melting  zinc  slime  are  sodium  carbonate  (NaaCOs), 
sodium  bicarbonate  (NaHCO3),  potassium  carbonate  (K2CO3), 
or  potassium  bicarbonate  (KHCO3),  preferably  the  carbonates 
of  sodium,  and  of  these  the  sodium  carbonate  which  is  1|  times 
stronger  than  the  sodium  bicarbonate.  The  sodium  and  po- 
tassium carbonates  and  bicarbonates  are  a  basic  flux  and  unite 
with  acid  fluxes  or  substances,  especially  with  silica,  to  produce 
a  sodium  silicate,  as: 

SiO2  =  Na2SiO3  +  CQ2. 


The  carbonates  fuse  between  800°  and  900°  C. 

Borax  and  Borax  Glass  as  Fluxes.  —  Borax  (Na2B4O7  .  10  H20) 
and  borax  glass  (Na2B4O7),  the  'anhydrous  borax  from  which  the 
water  of  crystallization  has  been  driven  off,  are  acid  fluxes  and 
unite  with  basic  fluxes  and  substances  to  form  a  borate  or  to 
dissolve  the  metallic  oxides  and  hold  them  in  the  slag  solution. 


186  TEXT  BOOK  OF  CYANIDE  PRACTICE 

The  formula  of  a  borate  may  be  written  Na2O  .  2  B2O3,  in  which 
the  boracic  acid  (B203)  acts  similarly  to  silica  (SiO2),  or  in  this 

way: 

ZnO  -f  Na2O  .  2  B2O3  =  Na2O  .  ZnO  .  2  B2O3. 

Silicates  and  borates  dissolve  together  to  form  what  may  be  termed 
silicate-borates,  which  will  lower  the  fusing  or  slag-forming  points 
and  promote  fusion  in  general.  Borax  melts  at  560°  C.  It  helps 
to  give  a  quick  fusion  and  a  liquid  slag.  Too  much  or  too  little 
borax  in  the  fusion  will  cause  a  thick  slag.  Borax  glass  has  nearly 
twice  the  strength  or  available  Na2B4O7  of  the  hydrous  borax. 

Silica  as  a  Flux.  —  Silica  (SiO2)  is  an  acid  flux  which  combines 
with  metallic  oxides  and  bases  to  form  silicates  containing  vary- 
ing quantities  or  proportions  of  silica.  Generally  the  higher  the 
proportion  of  silica  in  the  silicate,  the  less  fusible  or  fluid  it  is. 
Silica  itself  can  only  be  melted. at  a  tremendous  heat,  but  melts 
easily  with  a  basic  flux. 

Fluor  Spar  as  a  Flux.  —  Fluor  spar  (CaF2)  is  a  neutral  flux  that 
fuses  at  a  high  temperature.  It  is  but  little  used.  Its  chief 
value  is  to  give  fluidity  to  the  slag. 

Niter  as  a  Flux.  —  Niter,  potassium  nitrate  (KNO3),  is  a 
basic  flux  fusing  at  339°  C.  It  is  used  to  oxidize  the  base  metals 
that  they  may  more  readily  pass  into  the  slag  as  a  silicate, 
borate,  or  dissolved  metallic  oxide,  instead  of  into  the  bullion 
in  a  metallic  state.  It  is  especially  valuable  for  oxidizing  zinc 
when  the  same  has  not  been  effected  by  roasting,  or  the  zinc 
removed  by  acid  treatment.  It  does  not  so  readily  oxidize 
lead  and  the  other  metals,  as  it  gives  off  its  oxygen  at  too  low  a 
heat.  Niter  in  the  process  of  oxidizing  gives  off  its  acid  portion 
leaving  the  base,  potassium,  which  actively  combines  with 
silica  to  form  a  potassium  silicate  and  will  abstract  the  siliceous 
matter  of  the  crucible  if  silica  is  not  otherwise  available,  and  is 
assisted  in  this  by  the  oxidizing  influence  of  the  acid  portion  on 
the  carbon  of  the  crucible. 

Manganese  Dioxide  as  a  Flux.  —  Manganese  dioxide  (Mn02) 
is  a  basic  flux  and  oxidizing  substance,  as  niter,  but  is  not  as 
destructive  to  the  crucible.  It  is  a  better  oxidizer  of  lead  than 
niter,  though  with  silver  bullion  it  causes  more  silver  to  enter 
the  slag. 

Determining  the  Flux  to  be  Used.  —  The  flux  for  a  precipitate 
cannot  be  calculated  in  a  practical  way.  A  method  that  has 


FLUXING  AND  MELTING  187 

been  used  is  to  prepare  test  charges  of  precipitate  and  flux, 
smelt  them  in  assay  crucibles  in  the  assay  furnace,  and  observe 
the  resulting  slag  and  button,  probably  assaying  or  panning  the 
slag  to  find  how  low  in  value  it  is.  This  method  is  rather  un- 
satisfactory, for  the  fusion  in  an  assay  furnace  is  a  quick  one  at 
a  high  heat,  as  against  the  slow  and  lower  heat  when  melting  on 
a  working  scale.  Also  the  extent  to  which  the  charge  will 
abstract  silica  from  the  graphite  crucible  cannot  be  well  deter- 
mined; in  fact,  a  higher  silicate  containing  a  larger  proportion 
of  silica  will  generally  be  made  in  the  assay  furnace  fusion. 
In  preparing  the  flux  for  a  precipitate  at  a  new  plant,  past 
experience  is  relied  upon  in  connection  with  a  careful  observation 
of  the  conditions  under  which  the  precipitate  has  been  prepared, 
to  indicate  the  quantity  and  proportions  of  the  flux  to  be  used. 
The  melting  is  watched  and  studied,  the  effect  of  the  flux  on  the 
crucible  is  noted,  the  slag  is  examined  for  its  character  and  later 
assayed,  and  any  necessary  flux  added.  In  this  way  a  formula 
for  the  flux  is  worked  out. 

The  flux  must  be  varied  according  to  what  is  to  be  slagged 
off,  and  it  would  appear  that  the  proper  way  to  discuss  the 
proportions  would  be  to  take  a  type  of  flux  and  vary  it  to  meet 
the  different  requirements,  for  an  examination  of  the  formulae 
given  by  various  authorities  gives  little  information,  except  as 
the  proportions  are  varied  to  meet  variations  in  the  precipitate. 
The  following  is  given  as  the  normal  extremes  of  a  well  propor- 
tioned flux  that  has  been  found  very  satisfactory: 

Low  High 

Precipitate 100  parts.  100  parts. 

Borax  glass 12  parts.  30  parts. 

Sodium  carbonate 6  parts.  15  parts. 

Silica 3  parts.  8  parts. 

The  borax  glass  (or  equivalent  of  borax)  as  an  acid  flux  unites 
with  the  bases  and  oxides  of  the  base  metals  to  form  borates, 
it  also  dissolves  the  metallic  oxides  that  they  may  remain  sus- 
pended in  the  slag.  The  sodium  carbonate  (or  sodium  bicar- 
bonate or  the  potassium  carbonates)  as  a  basic  flux  unites  with 
the  acid  constituents  which  are  mainly  if  not  entirely  silica, 
forming  a  sodium  (or  potassium)  silicate  which  acts  as  a  flux  on 
bases  and  metallic  oxides  for  which  sodium  or  potassium  alone 
is  not  a  flux.  The  silicates  acting  with  the  borates  as  silicate- 


188          TEXT  BOOK  OF  CYANIDE  PRACTICE 

borates  lower  the  melting  point  of  the  charge  and  assist  in  the 
fusion;  their  increased  complexity  more  readily  dissolving  and 
holding  suspended  the  slag  constituents  of  the  charge.  The 
silica  unites  with  the  soda  and  the  base  oxides  to  form  various 
silicates,  so  that  the  slag  is  partly  a  complex  solution  of  vari- 
ous silicates,  a  thing  which  assists  the  fusion.  It  would  appear  at 
first  that  sodium  carbonate  being  a  base  should  not  be  added  to 
the  precipitate  which  is  basic  itself,  that  only  borax  and  silica 
should  be  added,  but  it  is  found  that  the  formation  of  a  certain 
amount  of  sodium  silicates  by  the  addition  of  soda  is  desirable 
to  get  a  rapid  and  satisfactory  fusion  at  low  heat.  For,  as  men- 
tioned before,  sodium  silicates  are  a  flux  for  the  bases  and  metallic 
oxides,  as  in  the  formula  Na2O .  ZnO .  SiO2  of  a  sodium  zinc 
silicate.  Soda  is  a  desulphurizer  and,  consequently,  may  be 
useful  for  that  purpose  with  a  precipitate  containing  sulphur  as 
a  sulphide.  Fine  quartz  tailing  or  other  sand  high  in  silica  is 
generally  used  to  supply  the  silica.  Ground  glass,  assay  slag, 
and  less  preferably  the  slag  from  previous  meltings  is  sometimes 
used.  These  are  already  complex  silicates  and  easily  fused, 
but  had  best  be  dispensed  with  in  favor  of  silica  and  sodium 
carbonate,  as  giving  more  desirable  silicates  and  a  greater 
effect. 

A  fluxed  charge  may  be  considered  to  be  divided  into  two 
components,  acid  oxides  and  basic  metallic  oxides,  which  are  to 
be  fused  to  a  liquid  neutral  slag.  The  acid  oxides  consist  of  the 
silica  (SiO2)  and  the  boracic  acid  or  boron  oxide  (B203)  of  borax, 
which  are  supplied  as  a  flux.  The  basic  metallic  oxides  are  the 
constituents  of  the  precipitate  outside  of  the  gold  and  silver,  to 
which  is  added  sodium  carbonate  (Na2C03)  that  its  sodium 
oxide  (Na20)  may  form  the  desirable  sodium  silicates  with  the 
silica  to  act  as  an  acid  flux  and  carrier  for  the  bases. 

Variations  Due  to  Zinc  and  the  Use  of  Oxidizers.  —  The  low 
amount  of  flux  in  the  formula  given  before  will  give  a  high-grade 
bullion  on  a  precipitate  containing  60  to  80  per  cent  of  bullion 
and  not  roasted  or  acid  treated,  such  as  that  screened  through 
a  40  or  60-mesh  screen.  As  the  amount  of  zinc  increases,  the 
amount  of  the  flux  must  be  increased  or  more  zinc  will  enter 
the  bullion.  The  low  amount  of  flux  will  give  a  slag  containing 
considerable  of  the  precious  metals  and  quite  often  some  matte. 
So  that  it  is  more  suitable  and  economical  for  a  silver  than  for 


FLUXING  AND  MELTING  189 

a  gold  plant,  which  would  use  more  flux,  perhaps  to  the  extent 
of  the  high  amount  and  more  when  the  percentage  of  bullion 
obtained  is  low  and  the  base  metals  are  in  a  metallic  form. 

Where  the  amount  of  zinc  is  high  and  it  has  not  been  oxidized 
through  roasting  but  tends  to  enter  the  bullion,  from  3  to  10 
per  cent  of  niter  may  be  added  to  the  precipitate,  —  even  20  per 
cent  has  been  used  when  the  slime  contained  lead,  —  for  the  pur- 
pose of  oxidizing  the  base  metals.  Manganese  dioxide  has  been 
used  in  quantity  up  to  40  per  cent  and  is  especially  recommended 
for  oxidizing  lead  which  usually  enters  the  precipitate  through 
the  zinc-lead  couple,  and  if  not  oxidized  and  slagged  off  or  com- 
bined with  sulphur  as  a  matte  —  a  sulphide  of  a  base  metal  — 
will  enter  the  bullion.  The  manganese  base  of  the  manganese 
dioxide  does  not  appear  to  so  actively  combine  with  silica  as  the 
potassium  base  of  niter  does,  and  consequently  does  not  attack 
the  crucible  to  such  an  extent.  Graphite  crucibles  are  usually 
made  of  one  part  of  fire  clay  and  two  of  graphite,  the  clay  acting 
as  a  binder  to  give  form  and  plasticity.  Clay  is  practically  a 
silicate  of  alumina  and  the  potassium  base  set  free  by  the  niter 
in  its  oxidizing  action  will  act  upon  the  clay,  unless  plenty  of 
silica  be  otherwise  present,  thereby  corroding  and  destroying 
the  crucible,  which  is  assisted  by  the  oxidizing  of  the  carbon  by 
the  niter  or  manganese  dioxide.  The  use  of  niter  or  manganese 
dioxide  in  the  flux  is  generally  avoided  by  thoroughly  roasting 
or  acid  treating  the  precipitate.  Their  use  involves  considerable 
care  so  that  the  experienced  melter  prefers  to  dispense  with  them 
or  use  clay  liners  in  the  graphite  crucible  when  using  a  large 
amount  of  the  oxidizers.  When  used,  an  amount  of  sodium 
equal  to  the  potassium  or  manganese  should  be  omitted. 

A  large  amount  of  zinc  is  also  taken  care  of  through  the  use 
of  plenty  of  silica  and  soda  to  form  a  zinc  silicate  or  sodium  zinc 
silicate;  the  amount  or  proportion  of  the  silica  should  be  kept 
high  or  it  will  be  abstracted  from  the  crucible,  for  zinc  silicate 
has  a  corrosive  action  upon  crucibles.  The  soda  is  also  valuable 
in  this  way  by  having  an  oxidizing  influence  on  the  zinc  and 
giving  a  liquid  slag.  But  as  borax  also  fluxes  the  zinc  by  the 
formation  of  a  borate,  it  should  be  used  together  with  the  soda 
and  silica  and  to  jointly  assist  by  the  formation  of  silicate- 
berates,  more  especially  when  the  zinc  is  in  the  form  of  an  oxide 
as  borax  has  a  high  dissolving  effect  on  the  oxides.  When 


190  TEXT  BOOK  OF  CYANIDE  PRACTICE 

metallic  zinc  is  present,  it  bubbles  and  boils  off  at  a  high  tempera- 
ture with  dense  fumes  of  zinc  oxide,  which  may  cause  a  loss  by 
carrying  off  the  precious  metals. 

General  Variations  and  Fluxing  Procedure.  —  The  presence 
in  metallic  form  of  other  metals  than  zinc,  and  other  reducers, 
call  for  similar  treatment  as  zinc.  If  the  precipitate  contains 
much  sand,  the  silica  in  the  flux  is  lessened  or  dispensed  with. 
The  presence  of  a  large  amount  of  lime  would  call  for  an  increase 
in  the  silica  or  borax,  or  the  use  of  less  soda.  The  addition  of 
soda  will  increase  the  fluidity  of  the  charge,  but  an  excess  of 
soda  or  its  addition  without  sufficient  silica  in  the  charge  must 
be  guarded  against  on  account  of  its  corrosive  action  on  the 
crucible.  It  should  always  be  borne  in  mind  that  soda  is  hard 
on  a  crucible.  Borax  increases  the  fluidity  under  normal  con- 
ditions, but  too  large  an  excess  makes  the  slag  thick  Borax 
should  be  used  to  thin  the  charge  and  give  fluidity  when  the 
silica  is  not  in  excess  —  when  the  slag  is  not  stringy  —  its  use 
for  that  purpose  is  preferable  to  soda  as  it  is  not  destructive 
to  the  crucible.  Silica  in  the  quantity  giving  a  neutral  slag 
gives  a  fluid  charge,  which  increases  in  pastiness  as  the  amount 
of  silica  is  increased.  The  higher  the  silica,  the  less  corrosion 
of  the  crucible.  Where  the  charge  is  too  thick  from  excess  of 
silica,  it  should  be  thinned  down  by  the  addition  of  soda.  An 
acid  or  siliceous  slag  is  stringy,  can  be  pulled  into  long  strings 
when  cooling,  and  is  glassy  and  brittle  when  cold.  A  basic 
slag  is  "  short,"  cannot  be  pulled  into  strings  when  melted  or 
cooling,  and  is  stony  and  dull  looking  when  cold.  Raising  the 
temperature  liquefies  the  pastiness  due  to  a  high  percentage  of 
silica,  and  makes  the  slag  more  fluid  in  general.  A  noncorrosive 
slag  at  a  red  heat  may  attack  the  crucible  at  a  white  heat,  because 
the  higher  the  heat  the  higher  will  be  the  silicate  formed,  but 
this  corrosion  increases  with  the  time,  for  the  higher  silicates 
are  slowly  formed  in  this  way.  The  appearance  of  graphite  in 
the  slag  indicates  that  the  crucible  is  being  attacked  and  that 
more  silica  should  be  added  to  the  charge.  The  addition  of 
glass,  assay  slag,  or  fluor  spar  should  thin  down  the  charge  with- 
out materially  varying  the  acid  or  basic  qualities  of  the  slag,  at 
least  not  to  the  unsafe  side,  and  may  be  preferable  to  the  practice 
of  adding  lime  with  a  corresponding  amount  of  borax  and  silica 
to  confer  fluidity  and  complexity. 


FLUXING  AND  MELTING  191 

The  fusion  must  be  carried  on  for  some  time  after  the  charge 
has  subsided  and  settled  in  a^  quiet  fusion,  to  insure  all  the  con- 
stituents being  decomposed  or  in  a  homogeneous  slag,  and  the 
precious  metals  fused  and  settled  into  the  bullion  in  the  bottom 
of  the  crucible.  Shots  of  precious  metal  throughout  the  slag  or 
settled  on  top  of  the  bar  indicate  too  thick  a  slag,  owing  to  an 
insufficiency  or  wrong  proportion  of  flux  or  to  too  low  a  heat. 
Bullion  of  a  high  degree  of  fineness,  a  rich  slag,  and  a  high  cost 
of  treatment,  fluxing,  and  melting  go  together.  Dehydrated 
or  anhydrous  fluxes,  those  free  from  moisture  and  water  of 
crystallization,  have  been  generally  recommended  that  loss  by 
ebullition  and  boiling  may  be  minimized,  but  the  success  being 
attained  in  melting  partly-dried  precipitate  will  cause  less  atten- 
tion to  be  paid  to  this.  Oxidizers  especially  cause  boiling  and 
ebullition.  Clay  liners  set  inside  of  graphite  crucibles  have 
been  used  to  lessen  the  corrosive  effect  of  the  slag.  Their  use 
causes  a  long  and  slow  fusion  with /a  large  quantity  of  flux,  so 
that  they  are  but  little  used.  They  are  valuable  when  using 
an  oxidizing  agent,  as  niter  or  manganese  dioxide. 

Matte  Formation.  —  A  matte  is  a  combination  of  sulphur  with 
a  base  metal  as  a  sulphide.  It  may  be  formed  artificially  by 
adding  sulphur  if  the  base  metals  are  present,  as  they  usually 
are,  or  by  adding  iron  if  the  sulphur  is  present.  With  both 
sulphur  and  base  metals  in  the  precipitate,  it  forms  naturally. 
The  sulphur  in  the  precipitate  may  be  principally  as  zinc  sul- 
phate due  to  poor  washing  of  the  precipitate  after  acid  treat- 
ment, to  lead  and  calcium  sulphates  formed  by  acid  treatment 
and  insoluble,  and  to  insoluble  sulphur  compounds  deposited 
in  the  zinc  boxes.  The  removal  of  the  bases  by  acid  treatment, 
the  oxidation  of  the  bases  and  sulphates  by  roasting,  or  the  use 
of  an  oxidizer,  as  niter  or  manganese  dioxide,  reduces  the  amount 
of  matte  or  eliminates  its  formation.  The  use  of  an  excess  of 
soda  will  reduce  the  amount  of  matte  formed,  for  soda  is  a  de- 
sulphurizer,  while  the  basic  slag  formed  will  dissolve  the  matte 
and  hold  it  in  suspension.  A  matte  increases  the  fineness  of 
the  bullion  by  taking  into  itself  base  metals  that  would  other- 
wise enter  the  bullion.  It  lowers  the  value  of  the  slag  by  col- 
lecting gold  and  silver  into  the  matte  that  would  otherwise  be 
found  in  the  slag,  but  it  also  prevents  some  gold  and  silver 
from  entering  the  bullion. 


192  TEXT  BOOK  OF  CYANIDE  PRACTICE 

Annealing  of  Graphite  Crucibles.  —  The  graphite  crucibles 
must  be  thoroughly  annealed,  by  being  placed  in  a  warm  or  hot 
place  for  perhaps  a  week,  and  finally  by  being  slowly  brought  to 
a  high  heat,  to  drive  off  all  the  absorbed  moisture.  This  is  done 
by  placing  the  crucible  on  a  boiler,  stove,  or  furnace,  and  finally 
in  the  fire  box,  before  using  it  for  the  first  time.  If  this  is  not 
done,  the  sudden  heating  of  the  crucible  will  in  all  cases  crack 
off  part  of  it  by  an  explosion  resulting  from  the  steam  formed 
by  the  absorbed  moisture.  There  is  less  tendency  for  the 
crucibles  to  break  after  they  have  once  been  annealed,  but 
between  melts  they  should  be  kept  in  a  warm,  dry  place. 

Melting  Furnaces.  —  Two  types  of  melting  furnaces  are  used: 
the  stationary,  in  which  the  crucible  must  be  removed  by  a  pair 
of|tongs  in  pouring  the  bullion,  and  the  tilting  furnace,  in  which 
the  entire  furnace  with  the  contained  pot  is  tilted  for  pouring 
off  the  slag  and  bullion.  The  application  of  the  tilting  furnace 
to  the  melting  of  cyanide  precipitate  is  of  comparatively  recent 
origin  and  has  been  very  successful,  though  trouble  has  been 
encountered  in  some  cases  in  learning  the  best  method  of  hand- 
ling it.  Both  hard  fuel,  such  as  coal,  coke,  and  charcoal,  and 
soft  fuel,  as  oil,  distillate,  and  gasoline,  are  used.  Gasoline  or 
distillate  is  the  most  advisable  fuel  where  only  a  small  amount 
of  gold  bullion  is  to  be  melted  at  a  time,  as  the  furnace  and 
accessories  are  obtained  and  installed  at  small  cost.  For  plants 
of  some  size,  oil  or  cheap  distillate  is  the  most  satisfactory  and 
economical,  except  where  the  local  conditions  make  the  cost  of 
oil  or  distillate  inordinately  high  above  hard  fuel.  Liquid  fuel 
gives  a  higher  and  quicker  heat  with  less  labor  and  dirt  than 
hard  fuel,  but  is  more  severe  on  the  crucibles. 

Preparation  of  Precipitate  and  Flux.  —  The  precipitate  may 
be  only  partly  dried  before  putting  into  the  crucible.  This  will 
save  the  labor  and  loss  involved  in  drying  and  in  the  dusting 
when  mixing  with  flux,  but  care  must  be  used  in  the  melting  to 
add  the  precipitate  before  the  last  has  fused  down,  or  loss  by 
spitting  may  result.  Or  the  precipitate  may  be  thoroughly 
dried  before  placing  in  the  crucible,  the  flux  being  added  before 
or  after  the  drying.  In  some  cases  the  precipitate  is  partly,  but 
not  thoroughly  dried,  then  mixed  with  the  flux  and  made  into 
briquettes  by  a  briquetting  machine,  that  the  briquettes  may 
be  handled  without  loss  by  dusting.  When  the  precipitate  is 


FLUXING  AND  MELTING  193 

not  thoroughly  dried  but  is  melted  moist,  the  necessity  of  bri- 
quetting  is  small. 

The  amount  of  the  precipitate  is  weighed  or  estimated  for 
adding  the  necessary  amount  of  flux.  The  flux  may  be  added 
by  charging  it  and  the  well-dried  precipitate  into  a  closed  revolv- 
ing barrel,  by  spreading  it  over  the  precipitate  and  shoveling 
to  mix,  or  by  spreading  the  precipitate  and  flux  in  alternate 
layers  which  receive  some  further  mixing  when  being  trans- 
ferred to  the  crucibles.  A  thorough  mixing  of  the  flux  and  pre- 
cipitate is  good,  but  is  not  absolutely  essential.  If  it  tends  to 
cause  a  loss  by  dusting,  it  need  not  be  so  thoroughly  done. 

Melting  Procedure.  —  The  annealed  crucible  is  generally 
loaded  with  the  fluxed  precipitate  nearly  to  the  top  before  start- 
ing the  fire.  After  the  crucible .  becomes  heated  the  charge 
subsides  through  the  melting  of  the  precipitate  in  the  bottom, 
and  more  precipitate  is  added  as  space  is  made.  Care  is  taken 
to  add  the  precipitate  before  that  in  the  pot  has  fused  down, 
that  there  may  be  little  dusting  of  the  newly-added  fluxed  pre- 
cipitate. Often  a  little  borax  glass  is  spread  over  the  charge  to 
melt  quickly  and  prevent  loss  by  dusting  and  fumes.  When 
no  more  precipitate  can  be  added  to  the  pot,  the  top  of  the 
charge  is  allowed  to  fuse,  and  after  having  subsided  for  some 
time  into  a  quiet  fusion  is  stirred  with  an  iron  rod  previously 
made  red  hot  to  prevent  the  slag  and  metal  from  adhering  to 
it.  The  slag  and  fusion  are  critically  inspected  to  note  if  addi- 
tional flux  or  longer  heat  is  required. 

The  fusion  being  brought  to  the  proper  condition  for  pouring, 
by  the  application  of  sufficient  heat  for  a  period  long  enough  to 
bring  the  mass  into  quiet  fusion,  and  by  the  addition  of  any 
required  flux  to  vary  or  thin  the  slag,  it  is  well  stirred  with  the 
heated-iron  rod  to  settle  any  shots  of  metal  before  pouring. 
The  fusion  may  be  poured  into  a  conical  mold  or  into  a  regular 
bullion  mold,  allowing  the  slag  to  overflow  or  run  through  a 
slot  into  the  slag  mold,  while  the  precious  metals  sink  through 
the  slag,  to  be  held  in  the  bottom  of  the  bullion  mold.  The 
slag  only  may  be  poured  into  the  conical  or  slag  mold;  or 
the  slag  may  be  dipped  off  by  a  heated  assay  crucible  held  in 
a  pair  of  assay  tongs.  The  slag  may  be  granulated  for  easy 
sampling  and  shipping  by  being  slowly  poured  into  water. 
The  buttons  of  bullion  from  the  bottom  of  the  conical  molds 


194  TEXT  BOOK  OF  CYANIDE  PRACTICE 

or  the  slabs  from  the  bullion  molds  are  collected  and  melted 
together  to  form  the  bar  of  bullion  for  shipment,  or  if  the  bullion 
is  retained  in  the  pot  it  is  poured  after  the  final  fusion.  After 
the  slag  or  slag  and  bullion  have  been  poured,  fresh  precipitate 
is  charged  into  the  crucible  and  the  melting  continued.  In 
some  cases  before  pouring  the  bar  for  shipment,  the  slag  is 
dipped  off  and  some  attempt  made  to  refine  the  bullion,  it  being 
finally  cast  without  any  slag,  though  casting  a  bar  without  a 
covering  of  slag  appears  to  be  of  no  advantage,  in  fact  may 
cause  trouble  by  the  metal  sloughing  off  the  top  of  the  bar. 
The  mold  should  be  painted  with  a  lime  emulsion  or  a  carbon, 
as  a  mixture  of  lampblack  and  oil,  soot  from  burning  waste, 
etc.,  before  the  pouring  to  prevent  the  bullion  and  slag  from 
sticking  to  the  mold.  The  mold  must  also  be  well  warmed 
that  the  cold  mold  may  not  be  cracked  by  the  sudden  introduc- 
tion of  the  hot  metal,  and  that  the  slag  and  metal  first  introduced 
will  not  be  chilled,  so  that  a  good  bar  or  button  of  bullion  cannot 
be  secured. 

Treatment  of  Slag  and  Crucibles.  —  The  slag  obtained  and  the 
old  crucibles  all  contain  considerable  metal.  The  method  of 
securing  this  varies.  It  is  invariably  in  a  metallic  condition,  as 
shots.  The  material  may  be  run  through  the  crushing  mill 
and  perhaps  most  of  the  metal  caught  by  amalgamation.  It 
has  been  run  through  a  separate  stamp  battery,  when  the  quan- 
tity was  large,  to  be  concentrated,  the  concentrate  being  melted 
in  the  melting  furnace  and  the  residue  cyanided  or  shipped  to 
the  smelters.  It  has  been  charged  into  an  amalgamating  barrel 
and  amalgamated,  the  residue  being  cyanided.  Cyaniding  the 
residue  is  not  usually  very  efficient.  It  has  been  sacked  up  and 
shipped  to  the  smelters.  A  lesson  has  been  taken  from  smelter 
practice  by  pouring  the  slag  into  a  conical  mold  with  a  clay- 
stoppered  hole  a  few  inches  above  the  bottom  or  apex  of  the 
mold.  The  slag  is  tapped  by  removing  the  clay  plug  after  a 
shell  J  inch  thick  has  formed,  allowing  the  core  to  be  granulated 
for  milling  or  shipment  to  the  smelters  by  running  into  water, 
while  the  richer  shells,  into  which  much  of  the  shot  and  prills 
of  metal  have  settled,  are  treated  separately  or  used  as  flux  in 
melting  precipitate. 

Treatment  of  Matte.  —  Matte  forms  on  top  of  the  bar  of 
bullion  as  a  tough,  brittle  film  of  base  metal  and  sulphur.  It  is 


FLUXING  AND  MELTING  195 

usually  undesirable,  though  it  has  been  artificially  produced  for 
the  purpose  of  increasing  the  grade  of  the  bullion.  As  it  con- 
tains considerable  gold  and  silver,  it  should  be  saved  to  be  melted 
into  a  large  bar  and  shipped,  or  to  be  refined  at  the  plant.  It 
has  been  fused  with  borax  and  soda,  and  the  addition  of  niter 
to  oxidize  the  metals,  to  give  a  button  of  gold  and  silver  and  a 
matte  and  slag  of  very  low  value.  A.  E.  Drucker  *  gives  the 
following  method  of  obtaining  an  extraction  of  85  to  94  per  cent 
of  the  value  in  the  matte.  Alternate  layers  of  borax,  matte, 
and  cyanide,  all  finely  crushed,  are  put  into  a  graphite  crucible. 
The  crucible  is  heated  at  a  white  heat  for  two  or  three  hours 
until  the  charge  subsides  and  action  ceases,  when  the  thick  slag 
is  skimmed  off  and  the  contents  of  the  crucible  poured. 

Smelting  with  Litharge  and  Cupellation.  —  In  the  lead  smelting 
of  zinc  slime,  the  precipitate  with  or  without  acid  treatment  is 
dried  to  a  small  per  cent  of  moisture  and  mixed  with  litharge, 
borax,  silica,  and  powdered  coke.  The  fluxed  material  is  bri- 
quetted  to  enable  easier  handling  and  less  dusting.  The  bri- 
quettes are  melted  in  a  cupel  furnace,  the  resulting  slag  being 
drawn  off.  The  lead  that  has  been  reduced  with  the  gold  and 
silver  is  cupeled  off  as  litharge  by  means  of  a  current  of  air 
blown  across  the  molten  metal,  oxidizing  the  lead  to  litharge, 
which  is  drawn  off  to  be  ground  and  reused  in  the  next  melting. 
After  the  lead  has  been  removed  in  this  way,  the  fine  gold  and 
silver  is  allowed  to  cool,  when  it  is  removed,  cut  up,  and  melted 
in  the  usual  graphite  crucible  into  a  bar  of  high  fineness  for 
shipment.  The  slag,  cupel  bottoms,  sweepings,  and  by-products 
are  smelted  in  a  small  lead  blast  furnace,  the  lead  produced 
being  cupeled  later.  The  method,  like  the  zinc-dust  process  of 
precipitation,  is  well  adapted  for  large  plants  producing  a  con- 
siderable quantity  of  precipitate.  It  is  apparently  a  cheaper 
and  more  efficient  method  of  turning  the  precipitate  into  fine 
bullion  than  the  usual  practice. 

Assay  of  Zinc  Precipitate. f  —  Zinc  precipitate  maybe  assayed 
by  three  methods:  by  scorification,  crucible  fusion,  or  a  com- 
bination method  involving  preliminary  refining  by  acid.  In 

*  Mining  and  Scientific  Press,  May  18,  1907.  Recent  Cyanide  Practice, 
p.  260. 

fSee  C.  H.  Fulton  and  C.  H.  Crawford  in  Bull.  No.  5,  South  Dakota 
School  of  Mines. 


196  TEXT  BOOK  OF  CYANIDE  PRACTICE 

the  assay  by  scorification,  ^  to  TV  assay  ton  of  precipitate  is 
taken  to  70  grams  or  more  of  test  lead  and  a  cover  of  a  small 
amount  of  borax  glass.  The  crucible  fusion  may  be  made  with 
the  following  charge: 


TV  assay  ton  precipitate. 
70  grams  litharge. 
5  grams  sodium  carbonate. 

1  gram  flour  (or  other  reducer). 
5  grams  silica. 

2  grams  borax  glass. 


By  the  combination  method,  TV  assay  ton  or  more  of  precipitate 
is  boiled  for  a  continued  length  of  time  with  20  c.c.  sulphuric 
acid  and  60  c.c.  water,  finally  filtered,  washed,  dried,  incinerated 
at  low  heat,  and  residue  fluxed  and  fused  in  the  usual  crucible 
fusion. 

In  all  cases  the  slag  and  cupel  of  the  first  fusion  should  be 
ground  up,  fluxed,  and  fused  in  the  same  crucible  dr  scorifier, 
and  the  results  added  to  the  first  fusion. 


CHAPTER    XVI 
CYANIDATION  OF  CONCENTRATE 

THE  cyanidation  of  concentrate  or  the  separated  sulphide 
constituent  of  an  ore  involves  no  departure  in  principle  from 
standard  cyanide  practice,  but  simply  stress  upon  certain  parts 
of  the  manipulation  to  meet  the  abnormal  conditions  connected 
with  the  sulphide  and  its  treatment.  A  clean  gold  ore  with  the 
precious  metal  finely  divided  and  upon  the  breaking  planes  or 
faces  of  the  crystals  of  the  ore,  and  a  sulphide  with  the  metal  in 
a  coarse  state  and  interbedded  with  and  in  the  pyritic  crystals 
are  the  two  extremes,  of  which  the  base  or  pyritic  ores  being 
cyanided  to-day  are  an  intermediate.  The  methods  of  cyanid- 
ing  concentrate  include  roasting,  leaching,  agitation,  nitration, 
decantation,  oxidation,  and  fine-grinding  as  with  ordinary  ores. 
The  prominent  characteristics  to  be  considered,  are:  Precious 
metal,  especially  with  gold  ores,  is  usually  in  a  comparatively 
coarse  metallic  state,  susceptible  of  being  amalgamated  to  a 
certain  extent,  and  requiring  considerable  time  for  dissolution. 
The  holding  of  the  precious  metals  to  a  large  extent  within  the 
pyritic  crystals,  requiring  fine-grinding,  oxidation,  drying,  or 
roasting  to  liberate  the  value.  The  presence  of  iron,  copper, 
lead,  arsenic,  antimony,  etc.,  either  metallic  or  as  compounds, 
and  the  resultant  high  consumption  of  cyanide  and  the  tendency 
of  the  solution  to  foul.  The  necessity  of  meeting  the  high 
acidity  generated.  The  action  of  cyanide  and  alkalinity  upon 
the  sulphide  to  form  soluble  or  alkaline  sulphides  and  the  con- 
sequential necessity  of  supplying  oxygen.  The  quick  settling 
of  the  concentrate  and  its  tendency  to  pack  and  become  imper- 
meable. Its  comparatively  high  value  and  that  of  the  solutions 
resulting  from  its  treatment. 

Treatment  by  Percolation.  —  The  treatment  of  concentrate 
by  percolation  usually  requires  from  10  to  30  days  to  obtain  a 
good  extraction.  In  some  cases  the  concentrate  as  obtained 
is  stored  under  water  to  prevent  the  formation  of  ferrous  sul- 
phate and  sulphuric  acid  through  the  decomposition  of  the 

197 


198  TEXT  BOOK  OF  CYANIDE  PRACTICE 

pyrite.  Though  where  the  concentrate  is  not  to  be  finely  ground 
it  is  better  to  spread  it  out  to  dry,  as  this  causes  the  grains  of 
pyrite  to  fall  apart,  decompose,  and  allow  solution  to  enter  them, 
that  the  metal  may  be  better  dissolved.  If  the  concentrate,  as 
charged  into  the  leaching  vat,  contains  much  soluble  acidity, 
lime  may  not  be  added  to  it,  but  the  charge  water-washed  until 
drainings  indicate  no  acidity,  to  be  followed,  to  remove  the 
latent  acidity,  by  a  wash  of  water  saturated  with  lime  —  a 
saturated  solution  of  lime  water  will  contain  about  2J  pounds 
CaO  per  ton  —  until  the  drainings  show  some  alkalinity.  The 
latter  method  is  not  advisable  unless  the  cyanide  solution  can 
be  used  with  a  protective  alkalinity  high  enough  to  meet  the 
acidity  as  it  may  be  generated  in  the  charge,  which  would  be 
indicated  by  the  outflowing  solution  always  showing  a  protective 
alkalinity.  When  lime  is  added  to  the  concentrate  it  is  impossible 
to  say,  without  studying  each  case  in  detail,  what  quantity  should 
be  used  and  how  fine  it  should  be  crushed.  It  should  be  added  in 
quantity  and  crushed  to  such  a  mesh  that  its  alkalinity  will  be 
dissolved  and  given  off  at  the  same  rate  that  the  acidity  is 
generated.  This,  of  course,  cannot  be  satisfactorily  accom- 
plished. The  results  of  laboratory  tests  and  experience  with 
previous  charges  must  be  relied  upon.  With  a  gold  sulphide, 
from  3  to  10  pounds  of  lime  will  usually  be  sufficient;  this  had 
best  be  added  unslacked  and  crushed  to  a  10-mesh,  the  larger 
part  being  coarse  granules.  After  the  concentrate  and  lime 
have  been  charged  into  the  leaching  vat,  they  should  be  water- 
washed  until  the  drainings  show  alkalinity.  Any  lack  of  alka- 
linity through  the  slow  dissolution  or  insufficiency  of  the  lime 
should  be  met  by  alkalinity  in  the  water  wash  or  solution.  It 
is  inadvisable  to  dispense  with  water-washing  and  at  once  run  on 
weak  cyanide  solution,  as  a  better  neutralization  of  the  acidity 
is  made  and  all  the  soluble  compounds  are  removed  instead  of 
entering  the  cyanide  solution,  which  they  may  foul  and  make 
more  viscous,  and  finally  be  precipitated  in  the  zinc  boxes. 

The  charge  is  drained  after  the  drainings  show  alkalinity, 
when  the  first  cyanide  solution  is  run  on,  preferably  one  low  in 
cyanide  and  strong  in  alkalinity.  The  weak  solution  is  run  on 
once,  or  for  a  short  time,  until  it  is  apparent  that  the  active 
cyanicides  have  been  met  and  the  strong  cyanide  solution  will 
not  be  too  quickly  destroyed,  after  which  strong  standardized 


CYANIDATION  OF  CONCENTRATE  199 

solution  is  used  until  the  dissolution  is  accomplished,  with 
final  washes  of  weak  solution  and  water.  The  strength  of  the 
strong  solution  will  vary  from  .2  per  cent  (4  pounds)  to  .75  per 
cent  (15  pounds),  seldom  higher;  a  strength  above  .5  per  cent 
(10  pounds)  is  generally  undesirable.  Strong  solutions  in  the 
presence  of  sufficient  oxygen  are  more  active  than  weaker  ones 
in  dissolving  the  precious  metals,  but  they  also  act  more  upon 
the  base  metals  and  compounds,  causing  them  to  enter  the 
solution  more  and  a  greater  consumption  of  cyanide.  Fresh 
strong  solution  should  be  constantly  supplied,  perhaps  by  con- 
tinuous leaching,  to  replace  about  each  particle  of  gold  that 
which  has  been  utilized  and  weakened  by  dissolving  coarse  gold 
or  neutralized  by  the  strong  cyanicides.  Each  strong  solution 
should  be  well  drawn  off  that  air  may  be  drawn  into  the  charge, 
both  to  assist  in  the  dissolution  of  the  precious  metals  and,  by 
oxidation,  to  decompose  and  break  open  the  pyrite  for  better 
contact  between  the  gold  and  silver  and  the  solution,  though 
this  is  bound  to  develop  considerable  acidity.  The  iron  and 
other  metallic  salts  from  the  decomposition  of  the  sulphide 
abstract  oxygen  from  the  charge  in  effecting  their  formation, 
and  by  supplying  plenty  of  oxygen  the  salts  are  finally  oxidized 
into  harmless  oxides  or  less  active  cyanicides,  as  the  oxidation 
of  ferrous  salts  into  the  ferric  oxide  or  hydrate.  The  first  solu- 
tion should  be  allowed  but  short  contact  with  the  charge  if 
rich  solutions  are  undesirable,  as  where  there  is  considerable 
leakage  or  they  go  directly  and  undiluted  to  a  zinc  box,  the 
shavings  of  which  they  would  coat  with  solid  metallic  gold  to 
cause  considerable  metallic  zinc  to  enter  the  melting.  Fresh 
solutions  are  necessary  to  supply  oxygen  to  get  quicker  dis- 
solution, consequently  continuous  leaching  with  periodical 
complete  drainings  to  aerate  the  charge  is  best.  It  is  not 
only  desirable  but  usually  essential  to  oxidize  artificially,  not 
by  chemical  oxidizers,  but  by  pumping  air  through  the  charge 
at  a  pressure  of  3  to  5  pounds  below  the  filter  bottom  when  the 
charge  is  drained.  It  is  not  advisable  to  draw  air  through  by 
means  of  a  vacuum  pump  applied  beneath  the  filter  bottom,  on 
account  of  packing  the  charge.  Leaching  charges  of  concen- 
trate should  be  shallow,  say  4  or  5  feet,  to  allow  of  easy  aeration. 
The  solutions  should  be  well  aerated,  which  may  be,  when  exces- 
sive aeration  is  desired,  by  means  of  an  air  cock  between  the 


200  TEXT  BOOK  OF  CYANIDE  PRACTICE 

pump  and  the  solution  tank  whereby  a  small  quantity  of  air 
is  drawn  in  and  pumped  with  the  solution,  or  by  allowing  a 
little  air  under  pressure  to  escape  into  the  solution  tank.  The 
solution  should  be  tested  for  its  reducing  power  and  for  alkaline 
sulphides.  It  may  be  advisable  when  about  half  the  treatment 
period  has  passed,  to  shovel  the  charge  over,  placing  the  bottom 
on  the  top.  This  is  an  excellent  method  of  aerating,  especially 
when  it  places  the  bottom  where  the  least  dissolution  has  taken 
place  owing  to  the  absence  of  oxidation  —  which  is  often  noticed 
in  treating  sulphide  —  on  top  where  the  greatest  dissolution  is 
effected.  However,  when  air  is  occasionally  pumped  through 
the  charge,  shoveling  over  may  be  more  beneficial  on  account 
of  the  packing  and  peculiar  cementing  or  caking  of  the  sulphide. 
To  lessen  the  tendency  to  pack  and  cake,  coarse  tailing  or  ore 
sand  may  be  mixed  with  the  concentrate. 

The  protective  alkalinity  of  the  inflowing  solution  should  be 
sufficient  to  give  a  slight  protective  alkalinity  in  the  outflowing 
solution.  Though  a  high  protective  alkalinity  is  necessary  to 
protect  the  cyanide  from  decomposition,  it  will  form  some 
soluble  or  alkaline  sulphides,  for  many  sulphides  are  acted  upon 
in  this  way  by  alkaline  solutions,  while  cyanide  decomposes 
these  and  other  sulphides  to  form  the  alkaline  sulphides.  The 
alkaline  sulphides  abstract  the  oxygen  necessary  for  dissolving 
purposes  and  in  weak  solutions  reprecipitate  silver,  and  perhaps 
gold  or  at  least  retard  its  dissolution,  so  that  they  should  be 
prevented  from  forming  or  should  be  gotten  out  of  the  solution 
when  once  formed.  These  are  removed  as  insoluble  sulphides 
by  the  zinc  in  solution  or  by  the  addition  of  lead  acetate.  The 
effect  of  adding  lead  acetate  occasionally  to  the  solution  to  the 
extent  of  a  total  of  one-half  to  one  pound  per  ton  of  concentrate 
should  be  studied,  even  if  no  alkaline  sulphides  are  ever  found 
in  the  solution.  Another  way  of  accounting  for  the  reduced 
extraction,  that  has  often  been  noted  when  using  a  high  pro- 
tective alkalinity  on  sulphide  gold  ore,  is  that  the  alkali  acts 
upon  the  pyrite  and  partly-decomposed  pyrite,  causing  a  gradual 
oxidation  into  ferric  oxide  (Fe203),  in  which  process  is  consumed 
a  large  amount  of  oxygen,  this  being  taken  from  the  solution 
causes  it  to  lose  its  dissolving  power.  Whether  the  cause  is 
the  reducing  action  of  alkaline  sulphides  or  of  ferrous  salts  or 
some  unknown  process,  it  is  apparent  that  aeration  is  a  most 


CYANIDATION  OF  CONCENTRATE  201 

important  thing.  The  effect  of  a  high  and  a  low  protective 
alkalinity  on  both  the  rate  and  extent  of  extraction  and  the 
consumption  of  cyanide  should  be  studied. 

Treatment  by  Agitation  and  Fine- Grinding.  —  Treatment  by 
agitation  will  usually  give  a  little  higher  extraction  than  leaching 
in  about  one-sixth  to  one-third  the  time,  and  with  a  less  con- 
sumption of  cyanide,  but  is  generally  carried  out  hi  connection 
with  fine-grinding.  The  fine-grinding  is  best  accomplished  in 
a  tube  mill  or  grinding  pan.  The  pulp  may  be  caused  to  flow 
over  amalgamating  plates,  for  in  some  cases  over  50  per  cent  of 
the  gold  may  be  secured  as  amalgam,  reducing  the  cost  and 
losses  in  the  subsequent  cyaniding,  and  probably  reducing  the 
time  of  dissolution  by  removing  the  coarse  gold.  Unless  the 
concentrate  contains  cyanicides  that  it  is  desirable  to  remove 
before  applying  the  cyanide,  it  may  be  advantageously  ground 
in  a  medium  cyanide  solution  —  about  .1  per  cent  (2  pounds). 
Mechanical  agitators,  unless  of  a  special  type  that  can  be  started 
while  raised  free  from  the  charge,  are  not  suitable  owing  to  the 
high  specific  gravity  of  the  concentrate  and  its  tendency  to  pack. 
Some  form  of  air  agitator  is  preferable,  and  in  all  cases  air  should 
be  supplied  during  the  agitation.  It  should  be  learned  how  the 
dissolution  progresses,  for  with  base  ores  it  has  been  noted  that 
after  the  passage  of  some  time,  the  rate  of  dissolution  rapidly 
falls  until  the  old  solution  is  removed  and  aeration  effected, 
when  new  solution  again  causes  a  rapid  dissolution.  If  supply- 
ing air  to  the  charge  does  not  cause  the  gold  to  go  into  solution 
with  the  maximum  rapidity,  the  charge  should  be  allowed  to 
settle,  the  clear  solution  syphoned  off,  and  new  solution  added 
for  further  agitation.  Treatment  of  slimed  sulphide  by  decan- 
tation  is  easy  as  it  rapidly  settles  to  a  small  bulk,  and  while  it 
gives  satisfactory  results,  the  up-to-date  plants  shorten  the  time 
of  treatment  by  filtering  the  pulp  after  the  bulk  of  the  value  has 
been  washed  out  by  decantation.  Most  of  the  leaf  filters  are 
unsuitable  for  handling  this  class  of  material,  since  on  account 
'of  Hie  high  specific  gravity  of  the  sulphide,  the  cake  must  be 
formed  within  a  few  minutes,  or  the  sulphide  will  settle  out  of 
the  solution,  and  owing  to  the  richness  of  the  solution  a  thorough 
and  highly-efficient  wash  must  be  given.  The  Kelly  filter  press 
making  a  cake  under  pressure  in  2J  to  5  minutes  is  now  in  satis- 
factory use  in  such  plants. 


202  TEXT  BOOK  OF  CYANIDE  PRACTICE 

General  Considerations.  —  Sliming  the  sulphide  should  be 
carried  as  far  as  possible,  as  giving  a  higher  and  quicker  extrac- 
tion. It  is  often  the  case  that  the  finer  concentrate  is  higher 
in  value  before  regrinding  and  treatment,  and  lower  in  value 
after  treatment  than  the  coarser  concentrate.  In  some  cases 
the  finely-ground  sulphide  may  be  mixed  with  coarse  sand  and 
successfully  leached,  though  agitation  is  better,  for  it  gives  a 
higher  extraction  than  leaching,  a  thing  that  is  not  noticeable 
with  gold  ores  but  holds  to  some  extent  with  silver  ores.  Treat- 
ment costs  by  agitation  are  generally  slightly  less  than  by  per- 
colation, for  the  less  consumption  of  chemicals,  due  to  lessened 
oxidation  and  formation  of  cyanicides,  overbalances  the  cost  of 
agitation.  A  plant  for  leaching  concentrate  is  comparatively 
inexpensive,  consequently  that  process  is  the  one  often  em- 
ployed by  small  operators,  whereas  with  a  large  amount  of  con- 
centrate to  be  treated  the  high  installation  cost  of  a  sliming 
and  agitation  plant  is  soon  met  by  the  increased  extraction. 
The  concentrate  after  treatment  often  contains  sufficient  value 
to  warrant  its  shipment  to  the  smelter,  if  the  original  heads 
were  extremely  high,  or  to  be  exposed  on  a  dump  for  retreat- 
ment  later,  after  it  has  oxidized,  or  by  some  new  process  yet  to 
be  devised  to  treat  this  class  of  material.  In  case  of  placing  on 
a  dump,  a  thorough  washing  should  be  given,  that  no  soluble 
cyanogen  may  be  left  remaining  to  effect  a  dissolution  that  will 
later  be  washed  out  by  rains  and  lost.  Many  plants  that  are 
now  shipping  their  sulphides  would  find  it  more  profitable  to 
first  treat  them  in  a  simple  leaching  plant,  or  more  expensive 
fine-grinding  and  agitating  plant,  before  shipping  the  residue; 
the  cost  of  treatment  being  offset  by  a  return  of  nearly  100  per 
cent  of  the  amount  extracted  by  cyanide,  instead  of  on  a  basis 
of  95  per  cent  as  paid  by  the  smelters,  and  the  lower  freight 
rate  and  smelter  charge  on  the  lower  grade  of  material  shipped. 
To  which  may  be  added  the  shrinkage  of  the  actual  value  and 
quantity,  which  is  made  by  the  smelters,  as  a  factor  of  safety  for 
their  own  protection  and  profit,  and  the  quicker  realization  of 
the  value  in  the  concentrate  when  produced  at  an  isolated  mine. 
In  some  cases  where  a  large  amount  of  concentrate  is  produced, 
it  might  be  advantageous  to  run  it  continuously  to  a  grinding 
mill  and  amalgamating  plates  and  ship  the  residue.  Treatment 
of  sulphide  involves  a  problem  as  to  whether  it  should  be  cyan- 


CYANIDATION  OF  CONCENTRATE  203 

ided  with  the  ore  or  removed  by  concentration  and  treated  sepa- 
rately. When  treated  with  the  ore,  much  of  the  dissolvable 
value  in  the  sulphide  is  not  obtained,  on  account  of  the  short 
treatment  given  the  ore,  but  this  may  be  more  than  offset  by 
the  cost  of  a  concentrating  plant  and  its  operation.  As  the 
sulphide  is  small  in  quantity  even  if  high  grade,  and  large  in 
quantity  but  low  in  grade,  treatment  of  it  in  the  ore  without 
concentration  becomes  more  advisable.  Fine  grinding  and  agi- 
tation of  the  ore  and  a  quick  dissolution  of  the  larger  part  of 
the  value  in  the  sulphide  make  for  treating  the  sulphide  in  the 
ore,  especially  where  means  are  provided  for  grinding  the  sul- 
phide finer  than  the  ore  in  general.  This  may  be  performed  by 
a  slow-speed  Chilian  mill  discharging  the  lighter  particles  by 
overflow,  or  by  returning  to  the  tube  mill  the  coarse  sand  and 
sulphide  separated  out  by  a  cone  classifier,  or  a  "  roughing  "  or 
concentrating  table  following  the  tube  mill  and  making  a  closed 
circuit  of  the  heavier  material.  A  determination  of  the  extrac- 
tion from  the  sulphide  with  varying  periods  of  treatment,  both 
when  contained  in  the  ore  and  as  concentrated  out,  will  give 
enlightenment  on  this  subject. 

Gold  concentrate  is  nearly  always  amenable  to  cyanide 
treatment.  Silver  concentrate  is  less  amenable,  but  important 
advancement  in  the  treatment  of  this  class  of  material  may  be 
expected.  Iron  pyrite,  zinc  blende,  and  galena  present  little 
interference  or  it  is  easily  met.  Arsenopyrite  or  mispickel, 
the  sulphide  of  arsenic,  may  usually  be  treated  satisfactorily  in 
large  quantities,  though  it  has  a  high  reducing  action.  Stibnite, 
the  sulphide  of  antimony,  often  causes  trouble  or  may  prevent 
successful  treatment.  It  is  an  active  reducer,  in  which  it  is 
similar  to  mispickel  but  much  more  pronounced  in  its  action, 
and  by  removing  the  oxygen,  through  the  formation  of  alkaline 
sulphides,  hinders  or  prevents  the  dissolution  of  the  precious 
metals.  It  also  holds  to  some  extent  the  precious  metals  in 
a  mechanical  combination  which  the  cyanide  cannot  break. 
Copper  in  unoxidized  pyrite  or  in  a  hard  state  is  but  little  acted 
upon  by  cyanide,  and  a  considerable  quantity  is  not  a  barrier 
to  successful  cyanidation,  but  when  in  a  soft  oxidized  state 
readily  dissolved  by  cyanide,  a  small  quantity  of  copper  may 
render  the  consumption  of  cyanide  too  high  and  require  special 
methods  of  treatment  and  precipitation. 


204  TEXT  BOOK  OF  CYANIDE  PRACTICE 

Where  the  sulphide  contains  a  large  amount  of  cyanicides 
which  are  not  removable  otherwise,  especially  iron  and  copper, 
a  preliminary  treatment  may  be  given  with  a  very  dilute  sul- 
phuric or  hydrochloric  acid  solution  to  remove  the  cyanicides. 
After  the  acid  has  performed  its  work,  the  soluble  salts  and  any 
excess  of  acid  remaining  are  removed  by  washing,  the  excess  of 
acid  to  be  used  on  the  next  charge.  The  acid  treatment  appears 
to  effect  a  decomposition  of  the  sulphide  to  give  a  higher  extrac- 
tion, in  addition  to  greatly  reducing  the  consumption  of  cyanide. 
It  would  appear  that  the  acid  solution  for  dissolving  or  altering 
the  cyanicides  could  be  prepared  very  cheaply,  by  passing  the 
sulphur  dioxide  (S02)  given  off  by  burning  sulphur  into  water 
to  form  sulphurous  acid,  as  is  done  in  making  sulphurous  acid 
for  the  acid  treatment  of  zinc  slime.  The  copper  in  the  acid 
solution  washed  out  of  the  ore  can  be  recovered  by  running  the 
solution  over  scrap  iron. 

Roasting  of  the  sulphide  will  usually  allow  a  high  extraction 
to  be  obtained  in  a  short  length  of  time  with  a  low  consumption 
of  cyanide.  It  has  been  generally  abandoned  in  favor  of  fine- 
grinding  and  agitation,  except  with  telluride  ores  where  the 
roasting  is  used  to  separate  the  tellurium  from  the  gold,  since 
gold  in  combination  with  tellurium  is  not  amenable  to  cyanide 
treatment  outside  of  the  bromocyanide  process  or  analogous 
chemical  processes.  In  the  bromocyanide  process,  the  addition 
of  bromine  to  cyanide  enables  the  cyanide  to  dissolve  gold  from 
telluride  and  arsenical  ores,  which  it  could  not  otherwise  do,  and 
increases  the  dissolving  efficiency  generally.  It  has  been  success- 
ful in  treating  sulphide,  though  but  little  interest  has  been  taken 
in  its  use  as  the  advantages  of  its  employment  are  usually  not 
warranted  by  its  increased  cost. 


CHAPTER  XVII 

\ 

ROASTING   ORE  FOR  CYANIDATION 

ORES  are  roasted  preliminary  to  cyanidation  in  two  distinct 
ways:  a  dehydrating  roast  to  remove  the  moisture  and  an  oxidiz- 
ing roast  to  remove  the  sulphur  or  tellurium  and  render  the 
cyanicides  innocuous.  The  dehydrating  roast  is  a  misnomer, 
for  the  process  is  simply  a  drying  one.  When  ore  to  be  dry- 
crushed  is  of  a  wet,  clayey,  talcose  nature  it  is  necessary  to 
remove  the  moisture  by  passing  the  ore  through  driers,  or  it 
will  clog  the  rolls  and  screens  and  be  poorly  sized.  This  drying 
process  dehydrates  or  drives  the  moisture  out  of  the  ore,  destroy- 
ing to  a  large  extent  the  adsorptive  and  flocculent  qualities  of 
the  clayey  matter,  making  it  less  plastic  and  more  granular  and 
leachable.  It  also  opens  the  capillaries  and  parting  planes  of 
the  more  crystalline  ore  so  that  it  is  more  easily  fractured  and 
crushed,  and  that  the  cyanide  solution  may  better  penetrate  it. 
The  influence  of  drying,  and  more  especially  of  roasting,  is  very 
marked  on  some  ores,  which,  due  to  the  large  amount  of  clayey 
matter  and  its  adsorbent  and  plastic  qualities,  will  adsorb  the 
cyanide  solution  and  refuse  to  allow  it  to  be  displaced  even  when 
mixed  with  much  coarse  material.  In  drying,  if  the  ore  con- 
tains much  sulphide,  a  high  heat  or  a  real  roasting  tendency 
cannot  be  allowed  —  unless  carried  to  a  "  dead  "  or  complete 
roast  —  owing  to  the  formation  of  ferrous  salts  and  other  cyani- 
cides. In  such  a  case  the  soluble  salts  or  free  acidity  should  be 
water-washed  out  of  the  ore,  and  the  insoluble  acidity  neutral- 
ized by  an  alkaline  wash.  The  dry  big  of  ore  followed  by  dry- 
crushing  was  formerly  much  in  vogue,  but  the  perfection  of 
fine-grinding,  agitating,  and  filtering  machinery  has  caused  a 
decline  in  the  practice,  especially  where  drying  and  fine-crushing 
are  necessary.  The  leaf  filter  is  well  adapted  for  handling  the 
clayey  slime,  which  formerly  gave  unsatisfactory  results  until  de- 
hydrated and  rendered  more  granular  and  leachable  by  roasting. 

The  oxidizing  roast,  while  rendering  the  ore  more  leachable 

205 


206  TEXT  BOOK  OF  CYANIDE  PRACTICE 

and  easily  crushed,  is  for  the  purpose  of  driving  off  the  sulphur 
as  sulphur  dioxide  (SO2),  thereby  converting  the  base  metals 
into  inert  oxides,  that  are  not  reducers  or  cyanicides,  and  liberat- 
ing the  gold  and  silver  mechanically  held,  or  for  driving  off  the 
tellurium  chemically  combined  with  the  precious  metals  in  a 
telluride  ore.  Due  to  the  high  insolubility  in  a  cyanide  solution 
of  gold  in  combination  with  tellurium,  such  ore  must  be  roasted 
before  being  cyanided,  though  bromine  is  used  in  connection 
with  cyanide  as  the  bromocyanide  process  in  Australia,  the 
bromine  giving  a  higher  solvent  effect  to  the  cyanide  solution. 

The  changes  occurring  in  the  roasting  of  an  iron  pyrite  (FeS2) 
may  be  given  as : 

FeS2  =  FeS  +  S. 

3  FeS  +  11  O  =  Fe2O3  +  FeSO4  +  2  SO2. 

2  FeS04  =  Fe2O3.+  SO3  +  SO2. 

It  is  necessary  that  a  complete  oxidizing  roast,  often  spoken  of 
as  a  "dead"  or  "  sweet "  roast,  be  given  the  ore  and  that  all 
the  sulphur  is  driven  off,  for  the  insoluble  ferric  oxide  (Fe203) 
finally  formed  is  not  affected  by  cyanide,  whereas  those  com- 
pounds formed  between  the  unoxidized  iron  pyrite  and  the  final 
ferric  oxide  may  be  considered  as  cyanicides.  In  this  way  the 
consumption  of  cyanide  is  reduced  and  the  amount  of  soluble 
salts  entering  the  solution  kept  at  a  minimum.  Telluride  ores 
are  roasted  until  the'  sulphide  content  is  fully,  oxidized.  The 
efficiency  of  the  roast  may  be  tested  by  taking  100  grams  or 
more  of  the  ore  and  shaking  for  a  few  minutes  with  the  same 
number  of  cubic  centimeters  of  water,  filtering  off  the  water 
and  slowly  adding  to  it  a  small  quantity  of  new  cyanide  solution 
of  the  working  strength.  If  no  cloudiness  appears,  the  ore  is 
dead  roasted  and  the  consumption  of  cyanide  due  to  cyanicides 
will  not  be  high,  but  if  a  discoloration  appears,  the  ore  still  con- 
tains soluble  salts  that  will  destroy  cyanide  and  foul  the  solution. 
Or  the  test  may  be  made  by  adding  a  few  drops  of  a  solution  of 
barium  chloride  (BaCl2),  which  will  indicate  soluble  sulphates 
by  forming  a  white  cloud  of  barium  sulphate  (BaSO4). 


^CHAPTER  XVIII 
CYANIDE    POISONING 

THE  poisonous  effects  of  cyanide  are  due  to  hydrocyanic  acid 
(HCN),  either  that  generated  in  the  working  of  the  process  or 
that  formed  by  the  acid  of  the  stomach,  when  cyanide  is  taken 
internally.  Hydrocyanic  acid,  or  prussic  acid  as  it  is  sometimes 
called,  is  one  of  the  most  deadly  poisons,  investigators  having 
been  killed  by  it  as  a  result  of  a  few  drops  of  the  liquid  acid 
falling  on  the  skin.  The  gas  or  the  vapor  of  the  acid  is  likewise 
poisonous,  producing  headaches,  dizziness,  and  nausea,  which 
slowly  pass  away  when  the  sufferer  is  removed  to  a  pure  atmos- 
phere, while  breathing  the  fumes  of  ammonia  will  afford  relief. 
Exposure  to  small  amounts  of  hydrocyanic  acid  gas  seldom 
causes  harm  beyond  possible  headaches,  depending  somewhat 
upon  the  susceptibility  of  the  person  exposed  to  it.  The  contact 
of  cyanide  solution  with  the  skin  tends  to  irritate  the  skin, 
cause  it  to  become  hard  and  crack,  and  may  cause  sores  and 
eruptions  —  a  species  of  eczema  —  though  with  the  weak  solu- 
tions now  in  use  there  are  seldom  harmful  results  unless  the  skin 
contains  open  wounds  or  cuts.  To  prevent  this  and  the  ends 
of  the  finger  nails  from  being  eaten  down,  rubber  gloves  are 
worn  when  working  in  solution,  as  when  cleaning  the  zinc  boxes. 
Or  the  hands  and  arms  are  given  a  coating  of  vaseline,  or  even 
the  stiff  lubricating  grease  used  in  mills,  to  render  the  contact 
between  the  skin  and  solution  less.  The  solution  should  always 
be  displaced  from  the  boxes  by  water  preliminary  to  cleaning- 
p,  to  lessen  the  danger  from  contact  with  it  and  the  hydro- 
yanic  acid  fumes  arising. 

Internal  Poisoning.  —  When  cyanide  as  in  a  solution  is  taken 
nternally,  the  acid  of  the  stomach  forms  hydrocyanic  acid  with 
t,  which  enters  the  blood  as  a  blood  poisoning,  paralyzing  the 
lervous  system  and  muscular  sensibility  and  suspending  the 
iction  of  the  heart.  The  hydrocyanic  acid  acting  in  the  blood 

207 


208  TEXT  BOOK  OF  CYANIDE  PRACTICE 

deprives  it  and  the  tissues  of  the  ability  to  absorb  oxygen, 
resulting  in  severe  cases  of  cyanide  poisoning,  of  the  sensation 
of  strangling,  and  inability  to  get  air  or  to  swallow.  With 
strong  solution,  or  when  having  taken  a  large  quantity  of  medium 
strength,  insensibility  results  almost  immediately,  and  death 
within  a  few  minutes.  Where  the  amount  taken  has  been 
small,  death  may  result  after  considerable  delay  and  suffering, 
if  an  antidote  is  not  at  once  administered.  Small  quantities  of 
weak  solution  are  not  necessarily  fatal,  but  unless  an  antidote 
is  used  the  risk  is  great. 

Treatment  by  Hydrogen  Peroxide.  —  In  a  case  of  poisoning, 
whether  by  the  vaporous  hydrocyanic  gas  causing  incipient 
insensibility  or  by  swallowing  cyanide  solution,  it  is  necessary 
to  act  with  all  speed  possible.  If  a  case  of  poisoning  by  being 
overcome  by  gas,  the  sufferer  should  be  removed  to  a  pure  atmos- 
phere, caused  to  breathe  the  fumes  of  ammonia,  and  given  a 
number  of  hypodermic  injections  of  a  3  per  cent  solution  of 
hydrogen  peroxide  (H202)  underneath  the  skin.  In  the  absence 
of  facilities  to  give  injections  a  10  per  cent  solution  should  be 
taken  in  internally  that  it  may  enter  the  blood  and  system. 
If  the  cyanide  has  been  taken  internally,  as  by  drinking  a  solu- 
tion, a  wineglass  or  more  of  a  30  per  cent  solution  of  hydrogen 
peroxide  should  be  taken  at  once,  and  subcutaneous  injections 
may  be  made  of  a  3  per  cent  solution.  The  patient's  throat 
should  be  tickled  with  the  finger,  or  more  preferably  by  a  soft 
rubber  hose,  to  cause  vomiting,  after  which  a  fresh  and  more 
dilute  solution  of  hydrogen  peroxide  should  be  given  and  the 
process  repeated.  Finally  water,  preferably  warm,  should  be 
taken  and  vomited  to  wash  out  the  stomach.  The  hypodermic 
injections  may  be  given  at  several  places  over  the  body,  and 
thereafter  at  intervals  one  minute  apart  and  gradually  lengthen- 
ing until  the  patient  is  relieved.  If  a  stomach  pump  is  available, 
the  stomach  should  be  pumped  out  after  each  dose  of  the  antidote 
or  wash.  In  case  the  patient  is  unconscious  and  only  able  to 
breathe  with  difficulty  or  not  at  all,  artificial  respiration  should 
be  induced,  as  in  a  case  of  drowning,  by  kneading  and  compress- 
ing the  body  and  pulling  the  arms,  chest,  and  abdomen.  Steps 
to  promote  the  circulation  may  be  taken  by  rubbing  and  knead- 
ing the  body.  Tickling  the  throat  is  perhaps  the  best  method 
to  produce  vomiting,  though  emetics  may  be  used,  such  as  a 


CYANIDE  POISONING  209 

spoonful  of  mustard  in  a  pint  of  warm  water,  if  they  can  be 
given  at  once  and  act  promptly. 

The  action  of  hydrogen  peroxide  (H2O2)  as  a  powerful  oxidizer 
is  to  form  an  oxamide  ((H2CNO)2)  with  the  hydrocyanic  acid  and 
a  cyanate  (KCNO)  with  the  cyanide,  which  are  harmless,  by 
decomposing  the  fiydrocyanic  acid  and  cyanide,  as: 

( 2  HCN  +  H202  =  (H2CNO)2. 
I  KCN  +  H2O2  =  KCNO  +  H2O. 

To  do  this  advantageously  it  must  be  introduced  before  the 
hydrocyanic  acid  or  cyanide  enters  or  is  absorbed  into  the 
system.  The  objection  to  the  use  of  hydrogen  peroxide  as  an 
antidote  when  cyanide  is  taken  internally  is  its  slow  action, 
which  may  allow  considerable  of  the  poison  to  enter  the  system 
before  the  decomposing  action  is  completed,  so  that  the  removal 
of  the  cyanide  and  the  washing  out  of  the  stomach  by  vomiting 
may  be  of  more  value  than  the  oxidizing  action  of  the  hydrogen 
peroxide. 

Treatment  by  Cobalt  Solution.  —  A  solution  of  nitrate  of 
cobalt,  or  other  salt  of  cobalt,  has  been  used  with  success  as 
an  antidote.  It  acts  almost  instantaneously  to  convert  the 
cyanide  into  an  insoluble  and  innocuous  cyanide  of  cobalt. 
But  an  excess  of  the  cobalt  salt  must  be  used  to  insure  the  imme- 
diate neutralization  of  the  cyanide,  which  requires  the  excess 
to  be  removed  by  vomiting  or  the  stomach  pump,  since  the 
nitrate  of  cobalt  itself  has  a  somewhat  poisonous  effect. 

Treatment  by  Ferrous  Salts.  —  The  quickest  and  best  method 
of  neutralizing  the  poison  when  it  has  been  taken  internally  is 
by  means  of  ferrous  hydrate  or  carbonate.  Due  to  the  fact 
that  these  decompose  quickly,  they  must  be  prepared  at  the 
time  when  used,  which  is  accomplished  by  making  up  the  follow- 
ing: 

A.  A  bottle  containing  1\  grams  ferrous  sulphate  (FeSO4) 

dissolved  in  30  c.c.  of  water. 

B.  A  wide-mouthed  bottle  with  a  capacity  of  about  400  c.c. 

containing  1J  grams  caustic  soda  (NaOH)  dissolved 
in  300  c.c.  of  water. 

C.  A  tube  or  phial  containing  2  grams  powdered  magnesia. 

These  three  bottles,  together  with  directions  for  their  use,  are 
kept  in  a  convenient  place  in  the  plant,  the  bottles  being  tightly 


210  TEXT  BOOK  OF  CYANIDE  PRACTICE 

corked  with  stoppers  that  can  be  instantly  removed.  In  a  case 
of  cyanide  poisoning  the  three  are  emptied  together  into  the 
larger  bottle,  well  shaken,  and  drunk  by  the  sufferer  from  the 
wide  mouth  of  the  bottle.  The  contents  of  the  stomach  should 
be  removed  and  washed  out  by  vomiting  or  the  stomach  pump. 
At  the  same  time  hypodermic  injections  of  hydrogen  peroxide 
may  be  given  under  the  skin,  if  the  case  is  serious,  to  reduce  the 
evil  effect  of  any  cyanide  that  has  entered  the  system.  The 
magnesia  is  used  to  increase  the  alkalinity  to  the  amount  re- 
quired to  overcome  the  acidity  of  the  stomach,  and  for  quick 
conversion  of  the  cyanide  into  a  ferrocyanide,  as  the  use  of 
caustic  alkali  to  that  extent  would  be  too  severely  caustic  on 
the  mucous  membrane.  The  caustic  soda  and  magnesia  may  be 
replaced  by  sodium  carbonate  (Na2CO3)  equal  in  weight  to  the 
ferrous  sulphate.  In  either  case  the  cyanide  is  converted  into 
a  ferrocyanide  (K4Fe(CN)6)  which  is  nonpoisonous,  as: 

FeSO4  +  2  NaOH  =  Fe(OH)2  +  Na2SO4. 
Fe(OH)2  +  6  KCN  =  K4Fe(CN)6  +  2  KOH. 

FeSO4  +  Na2CO3  =  FeCO3  +  Na2SO4. 
FeCO3  +  6  KCN  =  K4Fe(CN)6  +  K2CO3. 


In  all  cases  of  internal  cyanide  poisoning  the  poison  must  be 
removed  or  neutralized  and  removed  as  soon  as  possible.  Con- 
sequently, one  person  should  assist  the  sufferer  to  vomit,  using 
water  to  wash  out  the  stomach,  while  another  hurriedly  secures 
and  prepares  the  antidote.  Hydrogen  peroxide  is  one  of  the 
stock  articles  about  a  laboratory  and  should  always  be  found 
in  a  cyanide  plant,  to  fall  back  upon  in  emergency  if  no  other 
antidote  has  been  prepared.  It  should  be  kept  well  corked, 
covered,  and  in  a  dark  place  to  prevent  decomposition.  If  no 
antidote  is  at  hand,  washing  out  the  stomach  through  drinking 
watet  and  vomiting  by  tickling  the  throat  —  which  the  sufferer 
can  perform  alone  —  are  always  available. 

Poisoning  in  Precipitate  Refining.  —  Another  form  of  cyanide 
poisoning  is  that  due  to  the  gas  or  fumes  arising  in  the  acid 
treatment  of  zinc-box  slime.  The  fumes  are  principally  hydro- 
gen and  act  to  suffocate  the  person  exposed  to  them.  In  some 
cases  the  fumes  contain  hydrocyanic  acid  from  insoluble  cyanogen 
compounds  in  the  precipitate,  which  are  decomposed  by  the 


CYANIDE  POISONING  211 

sulphuric  acid;  this  will  result  in  greater  danger.  Where  arsenic 
has  been  deposited  in  the  boxes,  fumes  of  arseniureted  hydrogen 
will  be  given  off  when  treating  the  precipitate  with  sulphuric 
acid.  This  is  deadly  poisonous  and  has  resulted  in  a  number 
of  deaths,  in  one  instance  that  of  every  person  in  the  treatment 
house.  The  methbd  of  preventing  the  formation  of  this  arsen- 
iureted gas  has  been  given  under  Roasting  and  Acid  Treatment. 

The  treatment  of  acute  poisoning  or  the  distress  caused  by 
gas  consists  in  breathing  pure  air  and  the  fumes  of  ammonia. 
For  the  more  severe  cases  the  hypodermic  injections  of  hydrogen 
peroxide  and  the  promotion  of  artificial  respiration  will  un- 
doubtedly be  efficacious. 

Prevention  of  Poisoning.  —  Means  to  prevent  accidental 
cyanide  poisoning  should  be  taken  by  posting  a  sign  at  the 
works  calling  the  attention  to  the  use  of  cyanide  and  its  poisonous 
effects,  and  more  especially  that  pure  drinking  water  may  be 
obtained  at  a  certain  point,  which  should  be  labeled  and  removed 
from  the  vicinity  of  all  other  taps.  Promiscuous  drinking  from 
taps  and  hose  should  be  discouraged.  Care  should  be  taken 
in  planning  the  piping  that  cyanide  solution  may  never  pass 
into  the  water  pipes,  and  dependence  should  not  be  put  entirely 
upon  check  valves  for  this  purpose.  Care  should  also  be  used 
in  the  laboratory  and  elsewhere  that  cyanide  solution  contained 
in  pails,  vessels,  or  otherwise  may  never  be  mistaken  for  drinking 
water.  While  fatalities  from  drinking  cyanide  solution  are  rare, 
cyanide  solution  is  often  swallowed  by  mistake.  The  quantity 
so  taken  is  usually  small,  for  unless  the  drinker  is  in  a  hurry  and 
gulps  down  the  liquid,  he  at  once  detects  the  insipid  and  slightly 
salty  taste  of  weak  cyanide  solution.  No  harmful  results  follow 
when  an  antidote  is  immediately  taken,  except  that  due  to  the 
agitated  state  of  mind  and  the  vomiting.  Workmen  who  are 
troubled  with  or  subject  to  cyanide  eczema  or  disorders  due  to 
cyanogen  should  be  transferred  to  other  work. 

Ventilating  an  enclosed  cyanide  plant  is  often  desirable  to  re- 
move the  hydrocyanic  acid  fumes  arising.  Trouble  is  sometimes 
encountered  in  working  in  deep  tanks  in  which  hydrocyanic 
acid  has  accumulated,  especially  with  pyritic  ores  generating 
acidity.  A  closed  or  partly-closed  tank  that  has  held  cyanide 
solution  should  never  be  entered  or  death  will  usually  result 
from  the  hydrocyanic  acid  it  contains.  Working  in  the  presence 


212  TEXT  BOOK  OF  CYANIDE  PRACTICE 

of  obnoxious  or  dangerous  gases  may  be  rendered  less  harmful 
by  displacing  the  air  and  working  in  the  presence  of  air  sup- 
plied under  pressure  through  a  hose.  Hoods  and  good  ven- 
tilation should  be  provided  in  the  precipitate  refining  house  to 
carry  away  the  fumes,  for  a  man  who  has  once  been  "  gassed," 
as  most  cyanide  workers  have  been,  is  very  susceptible  to  it 
thereafter,  and  a  slight  touch  may  physically  incapacitate  him 
for  a  day  or  more. 

Cows  are  easily  poisoned  by  drinking  the  diluted  solution  or 
moisture  from  the  discharged  residue  or  by  licking  the  salts 
resulting  from  the  evaporation  of  such  moisture;  horses  are  not 
so  often  poisoned  and  pigs  very  seldom.  The  addition  of 
copperas,  the  commercial  term  for  ferrous  sulphate  (FeS04),  or 
other  cyanicide  to  the  moist  tailing  has  lessened  the  trouble  in 
this  direction. 


CLASSIFIED  BIBLIOGRAPHY 

A.  Books.  PAGE 

1.  Treatises  on  cyanidation 215 

2.  Treatises  in  part  on  cyanidation 215 

3.  Treatises  in  part  on  special  topics  of  cyanidation 216 

B.  History  and  progress 217 

C.  Chemistry  and  physio-chemistry  of  cyanidation 218 

D.  Aeration  and  oxidation 221 

E.  Commercial  cyanide  and  its  analysis 222 

F.  Analytical  chemistry  of  cyanide  solution 223 

G.  Assaying,  samplers,  and  sampling 225 

H.  Ore  testing  and  physical  tests 226 

7.    Alkalinity  and  lime 228 

J.   Classification,  de watering,  and  slime  settlement 228 

K.  Sand  treatment  and  percolation 230 

L.   Slime  treatment,  agitation,  and  decantation 231 

M.  Filtration 235 

N.  Precipitation 238 

0.   Cleaning-up,  refining,  and  melting 242 

P.   Telluride  ore,  roasting,  bromocyanide,  and  chlorination 244 

Q.   Cupriferous  ore  and  solution 246 

R.   Concentrate  cyanidation 247 

S.   Other  refractory  ores 248 

T.  Cyanide  poisoning 249 

U.  Construction,  and  pulp  and  residue  conveying  and  disposal 250 

V.  Tube-milling  and  fine-grinding 252 

W.  Cyanidation  of  silver  ores,  and  in  Mexico 256 

X.  Cyanidation  in  United  States  and  Canada. 

1.  Nevada 260 

2.  Black  Hills 261 

3.  Outside  of  Nevada  and  Black  Hills 262 

F.   Cyanidation  in  South  Africa 264 

Z.   Cyanidation  in  Australia 265 

Miscellaneous. . .  266 


213 


CHAPTER  XIX 
CLASSIFIED  BIBLIOGRAPHY 


A.  Books 

1.  TREATISES  ON  CYANIDATION 

BOSQUI,  F.  L.     Practical  notes  on  the  cyanide  process.     1900,  201  pp. 

CLENNELL,  J.  E.  The  chemistry  of  cyanide  solutions  resulting  from  the 
treatment  of  ores.  Second  edition,  1910,  202  pp. 

The  cyanide  handbook.     1910,  520  pp. 

EISSLER,  M.  The  cyanide  process  for  the  extraction  of  gold.  Third 
edition,  184  pp. 

GAZE,  WM.  H.     Practical  Handbook  of  Cyanide  Operations. 

JAMES,  ALFRED.     Cyanide  practice.     1901,  174  pp. 

JULIAN  (H.  F.)  and  SMART  (E.).  Cyaniding  gold  and  silver  ores.  Second 
edition,  1907. 

McCANN,  FERDINAND.  Beneficio  de  metales  de  plata  y  oro  por  cianuracion. 
(Reduction  of  gold  and  silver  ores  by  cyanidation.)  1910,  381  pp.  Printed 
in  Spanish. 

MEGRAW,  HERBERT  A.     Practical  data  for  the  cyanide  plant.     1910,  93  pp. 

MILLER,  ALFRED  S.     The  cyanide  process.     Second  edition,  1906,  95  pp. 

PARKS,  JAMES.  The  cyanide  process  of  gold  extraction.  Fourth  edition, 
1906,  239  pp. 

ROBINE  (R.)  and  LENGLEN  (M.).  Translated  by  J.  Arthur  Le  Clerc. 
The  cyanide  industry  theoretically  and  practically  considered.  (Dealing 
with  the  properties  and  manufacture  of  cyanide.)  1906,  408  pp. 

SCHEIDEL,  A.     The  cyanide  process.     1901,  140  pp. 

WILSON,  E.  B.     Cyanide  processes.     Fourth  edition,  1908,  249  pp. 

Recent  cyanide  practice.  (Compiled  by  T.  A.  Rickard  from  articles  on 
cyanidation  in  Mining  and  Scientific  Press  between  Jan.,  1906,  and  Oct.,  1907.) 
334  pp. 

More  recent  cyanide  practice.  (Compiled  by  H.  Foster  Bain  from  articles 
on  cyanidation  in  Mining  and  Scientific  Press  between  Oct.,  1907,  and  July, 
1910.)  418  pp. 

2.  TREATISES  IN  PART  ON  CYANIDATION 

AUSTIN,  L.  S.  The  metallurgy  of  the  common  metals.  Third  edition, 
1911,  528  pp.  (71  pages  on  cyanidation.) 

CHARLETON,  A.  G.  Gold  mining  and  milling  in  Western  Australia,  with 
notes  upon  telluride  treatment,  costs,  and  mining  practice  in  other  fields. 
1903,  648  pp.  (192  pages  on  cyanide  practice  in  Australia.) 

215 


216          TEXT  BOOK  OF  CYANIDE  PRACTICE 

CLARK,  DONALD.  Australian  mining  and  metallurgy.  1904,  531  pp. 
(Consisting  mainly  of  valuable  technical  descriptions  of  cyanide  practice  in 
Australia.) 

Gold  refining.  123  pp.  (Largely  on  the  refining  of  cyanide  precipitate. 
From  series  of  articles  ending  Jan.,  1908,  in  Australian  Mining  Standard.) 

EISSLER,  M.  The  metallurgy  of  gold.  Fifth  edition,  1900,  638  pp.  (90 
pages /on  cyanidation.) 

HOFFMAN,  O.  Hydrometallurgy  of  silver.  1907,  345  pp.  (42  pages  on 
cyanidation  of  silver  ores,  principally  an  abstract  of  practice  at  Palmarejo, 
Chihuahua,  Mexico,  from  T.  H.  Oxnam  in  T.  A.  I.  M.  E.,  vol.  36,  1905.) 

Louis,  HENRY.  Handbook  of  gold  milling.  (Chapter  on  the  cyanide 
process.) 

ROSE,  T.  KIRKE.  The  metallurgy  of  gold.  Fifth  edition,  1907,  534  pp. 
(90  pages  on  cyanidation.) 

International  Library  of  Technology  of  the  International  Correspondence 
School.  Vol.  21,  1902.  Metallurgy  of  gold,  silver,  copper,  and  lead.  531  pp. 
(94  pages  on  cyanidation.) 

The  Mineral  Industry.  Vols.  1  (1892)  to  19  (1910).  (Containing  an 
extremely  valuable  technical  review  of  cyanidation  by  years.) 

Proceedings  of  Chemical  and  Metallurgical  Society  of  South  Africa.  Vols. 
1  (1894-1897)  to  4  (1903-1904).  (Mainly  containing  valuable  technical 
articles  on  principles  of  cyanidation.)  (Later  proceedings  appear  unbound 
as  monthly  Jour.  Ch.,  Met.,  &  Min.  Soc.,  S.  A.) 

3.   TREATISES  IN  PART  ON  SPECIAL  TOPICS  OF  CYANIDATION 

ARGALL,  PHILIP  H.  Western  mill  and  smelter  methods  of  analysis.  1905, 
124  pp.  (Contains  analytical  methods  used  in  cyanide  plants.) 

BARR,  JAMES  A.  Testing  for  metallurgical  processes.  1910,  216  pp. 
(Contains  43  pages  on  testing  of  ores  for  cyanidation.) 

BROWN,  WALTER  LEE.  Manual  of  assaying.  (Contains  methods  of 
cyanide  testing.) 

FURMAN,  H.  VAN  F.  A  manual  of  practical  assaying.  (Revised  by  Pardoe.) 
Eighth1  edition,  1911,  530  pp.  (15  pages  on  testing  in  the  cyanide  process, 
also  other  allied  matter.) 

HUTCHINSON,  J.  W.  Operations  of  Goldfield  Consolidated  Mill.  (Re- 
printed in  pamphlet  form  from  M.  &  S.  P.,  May  6  to  June  10,  1911.) 

LODGE,  R.  W.  Notes  on  assaying.  Second  edition,  1906,  312  pp.  (20 
pages  on  cyanide  testing.). 

MACFARREN,  H.  W.  Practical  stamp  milling  and  amalgamation.  1910, 
166  pp.  (Contains  information  on  amalgamating  in  cyanide  solution,  mill 
tests,  and  relation  between  stamp-milling,  amalgamation,  fine-grinding,  and 
cyanidation.) 

RICHARDS,  R.  H.  Ore  Dressing.  Vols.  1  and  2,  pp.  1-1200,  1903;  vols.  3 
and  4,  pp.  1200-2052,  1909;  index  to  four  volumes,  112  pp.,  1909.  (Contains 
no  direct  matter  on  cyanidation,  but  much  allied  matter  on  crushing,  arrange- 
ment of  mills,  and  general  metallurgy.) 

SHARWOOD,  W.  J.  Measurement  of  pulp  and  tailing.  1910,  22  pp.  (Re- 
print from  Min.  Mag.,  Nov.,  1909,  to  Jan.,  1910.) 


CLASSIFIED  BIBLIOGRAPHY  217 

Notes  on  metallurgical  mill  construction.  (Compiled  by  W.  R.  Ingalls 
from  articles  in  Eng.  &  Min.  Jour.  Contains  information  on  tube-milling, 
fine-grinding,  construction,  conveying,  water-saving,  etc.)  1906,  256  pp. 

B.  History  and  Progress 

ARGALL,  P.  Historical  summary  of  steps  in  cyanidation.  Mines  &  Mins., 
vol.  28,  p.  368,  1  p. 

Limitations  of  cyanide  process.     Eng.  &  Min.  Jour.,  vol.  64,  p.  278. 

Metallurgical  progress  in  Colorado.     M.  &  S.  P.,  Jan.  1,  1910,  6  pp. 

Review  of  cyanidation  in  1910.     Eng.  &  Min.  Jour.,  Jan.  7,  1911,  4  pp. 

Steps  in  eyanidation.     Proc.  Colo.  Sci.  Soc.,  Nov.,  1907,  25  pp. 

BARBOUR,  P.  E.  Developments  in  cyanide  practice.  Mines  &  Mins., 
May,  1911,  4  pp. 

BROWNE,  R.  S.  Progress  in  cyano-metallurgy  during  1909.  Pac.  Miner, 
Jan.,  1910,  4  pp. 

Review  of  cyano-metallurgy  in  1910.     Pac.  Miner,  Jan.,  1911,  3  pp. 

DURRANT,  H.  T.  Limitations  of  cyanide  process.  M.  &  S.  P.,  Mar.  5, 
1904,  1  p.;  abstract  from  Jour.  Ch.,  Met.,  &  Min.  Soc.,  S.  A. 

FULTON,  C.  H.  Review  of  the  cyanide  process  in  United  States  during 
1902.  Eng.  &  Min.  Jour.,  Jan.  3,  1903,  4  pp. 

Cyanidation  in  United  States.     Eng.  &  Min.  Jour.,  Jan.  7,  1904,  2  pp. 

Cyanidation  in  United  States.     Eng.  &  Min.  Jour.,  Jan.  5,  1905,  3  pp. 

Cyanidation  during  1905.     Eng.  &  Min.  Jour.,  Jan.  13,  1906,  3  pp. 

(See  annual  reviews  in  The  Mineral  Industry.) 

GORDON,  R.  W.  Progress  in  cyaniding  during  1910.  Met.  &  Chem.  Eng., 
Jan.,  1911,  1  p. 

GUESS,  H.  A.  Progress  in  ore  dressing  in  United  States  and  Mexico  during 
1910.  Met.  &  Chem.  Eng.,  Jan.,  1911,  2  pp. 

JAMES,  A.  Improvements  in  cyanidation.  Eng.  &  Min.  Jour.,  Jan.  28, 
1904,  1  p. 

Progress  in  cyanidation  in  1906.  M.  &  S.  P.,  Jan.  5,  1907,  5  pp.  "Recent 
Cyanide  Progress, "  p.  197. 

Progress  in  ore  treatment  during  1906.  Eng.  &  Min.  Jour.,  Jan.  5,  1907, 
3pp. 

Progress  in  the  treatment  of  gold  ore.  M.  &  S.  P.,  Jan.  4,  1908,  2  pp. 
"More  Recent  Cyanide  Practice,"  p.  114. 

Progress  in  cyanidation.  M.  &  S.  P.,  Jan.  2,  1909,  7  pp.  "More  Recent 
Cyanide  Practice, "  p.  233. 

Progress  in  cyanidation.  Eng.  &  Min.  Jour.,  June  12,  1909,  1  p.;  Min. 
World,  June  12,  1909,  1  p. 

Annual  cyanide  letter.  M.  &  S/P.,  Jan.  1,  1910,  6  pp.;  discussion,  Feb.  26, 
Apr.  2,  and  May  28,  1910.  "More  Recent  Cyanide  Practice,"  p.  362. 

Progress  in  treatment  of  gold  and  silver  ores  during  1910.  M.  &  S.  P., 
Jan.  7,  1911,  5  pp. 

LAMB,  M.  R.  Progress  and  developments  in  cyanide  practice.  Eng.  & 
Min.  Jour.,  Jan.  15,  1910,  2  pp. 

MERRILL,  C.  W.  Present  limitations  of  cyanide  process.  T.  A.  I.  M.  E., 
vol.  25,  1895,  4  pp. 


218          TEXT  BOOK  OF  CYANIDE  PRACTICE 

NICOL,  J.  M.  Discussion  of  Leopoldo  Salazar's  paper  on  MacArthur- 
Forrest  cyanide  patents  in  Mexico,  and  lessons  to  be  learned  from  history  of 
subject.  Trans.  Mex.  Inst.,  Feb.,  1910,  8  pp. 

MACARTHUR,  J.  S.  Gold  extraction  by  cyanide.  (A  retrospect.)  Eng.  & 
Min.  Jour.,  Aug.  12,  1905,  1  p. 

McCoMBiE,  J.  History  of  cyanide  process.  (First  plants.)  M.  &  S.  P., 
June  24,  1911,  1  p. 

PAUL,  A.  B.     MacArthur-Forrest  process.     M.  &  S.  P.,  Jan.  21,  1893,  1  p. 
SALAZAR,    L.     MacArthur-Forrest    cyanide    patents    in    Mexico.     Trans. 
Mex.  Inst.,  Oct.,  1909,  6  pp. 

TRAPHAGEN,  DR.  F.  W.  Cyanide  process  —  a  review.  West.  Ch.  &  Met., 
Nov.,  1907,  6  pp. 

Mining  and  Scientific  Press.  American  progress  in  cyanidation  during 
1910.  Jan.  7,  1911,4pp. 

Bibliography  of  early  articles  and  books  on  cyanide  process.     Nov.  28, 
1896,  1  p. 

Cyanide  process.     July  2,  1892,  10  pp. 
MacArthur-Forrest  cyanide  process.     Vol.  65,  p.  3,  2  pp. 
MacArthur-Forrest  cyanide  process.     Vol.  66,  p.  36,  1  p. 

C.  Chemistry  and  Physio-Chemistry  of  Cyanidation 

ALDERSON,  M.  W.  Loss  of  gold  in  cyanidation  by  volatilization.  M.  & 
S.  P.,  Oct.  29,  1898,  1  p. 

ANDERSON,  I.  Regenerating  copper  cyanide  solution.  M.  &  S.  P.,  Feb.  5 
and  May  28,  1910,  1  p.  "More  Recent  Cyanide  Practice, "  pp.  352,  355. 

BECKMAN,  J.  W.     What  is  a  cyanamide  ?     M.  &  S.  P.,  Jan.  28,  1911,  1  p. 

BETTEL,  WM.  Osmotic  pressure,  disassociation,  and  electrolysis.  Proc. 
Ch.  &  Met.  Soc.,  S.  A.,  vol.  2,  1899,  8  pp. 

BURGGRAF,  J.  Efficiency  of  a  lead  salt  in  cyaniding.  Mex.  Min.  Jour., 
Oct.,  1911;  abstract  in  Min.  &  Eng.  World,  Nov.  18,  1911. 

CALDECOTT,  W.  A.  Cyanidation  of  silver  ores.  (Chemistry.)  M.  &  S.  P., 
Dec.  12,  1908,  1  p.  "More  Recent  Cyanide  Practice,"  p.  184. 

Precipitation  of  gold  and  silver  by  soluble  sulphides.  Eng.  &  Min.  Jour., 
Apr.  24,  1909,  1  p. 

Relative  efficiency  of  strong  and  weak  cyanide  solutions  for  dissolving  gold. 
Proc.  Ch.  &  Met.  Soc.,  S.  A.,  vol.  1,  1896,  3  pp. 

Some  features  of  silver  ore  treatment  in  Mexico.  Jour.  Ch.,  Met.,  &  Min., 
Soc.,  S.  A.,  Jan.,  1908,  3  pp.,  Mar.,  3  pp.,  May,  1  p.,  June,  1  p.,  July, 
3  pp.,  Sept.,  1908,  1  p.;  abstract  in  Eng.  &  Min.  Jour.,  June  27,  1908;  ab- 
stract in  M.  &  S.  P.,  Mar.  28,  1908,  2  pp.,  May  2,  1908,  3  pp.,  Aug.  29, 
1908,  2  pp. 

CAREY,  E.  E.     Clancy  process.     Pac.  Miner,  Nov.,  1910. 

Electrochemical  lixiviation.     Pac.  Miner,  Oct.,  1909,  2  pp. 

Electrochemical  system  of  amalgamation  and  cyanidation.  Eng.  Mag., 
Dec.,  1909,  7  pp. 

CARTER,  T.  L.  Notes  on  cyanide  solutions.  Eng.  &  Min.  Jour.,  vol.  73, 
P.  237,  1  p. 


CLASSIFIED  BIBLIOGRAPHY  219 

CHRISTY,  S.  B.  Electromotive  force  of  metals  in  cyanide  solutions.  T.  A. 
I.  M.  E.,  vol.  30,  1900,  83  pp. 

Solution  and  precipitation  of  gold.  T.  A.  I.  M.  E.,  vol.  26,  1896,  37  pp.; 
vol.  28,  1898,  25  pp.;  discussion  in  Proc.  Ch.  &  Met.  Soc.,  S.  A.,  vol.  2, 
1897. 

CLANCEY,  J.  C.     Clancey  process.     Min.  World,  Feb.  11,  1911. 

Cyanamide  process  in  the  metallurgy  of  gold.  Met.  &  Chem.  Eng.,  Jan., 
1911,  6  pp. 

CLENNELL,  J.  E.  Electrolytic  cyanide  regeneration.  Eng.  &  Min.  Jour., 
May  27,  1911,  3pp. 

COEHN  (A.)  and  JACOBSON  (C.  L.).  Passivity  of  gold.  M.  &  S.  P.,  Mar. 
28,  1908. 

CROSSE,  A.  F.  Regeneration  of  working  cyanide  solutions  where  zinc 
precipitation  is  used.  Proc.  Ch.  &  Met.  Soc.,  S.  A.,  vol.  3,  1903,  28  pp.; 
vol.  4,  July  and  Sept.,  1903,  8  pp.;  abstract  in  Eng.  &  Min.  Jour.,  May  30, 

1903,  1  p.;  discussion,  June  20,  Sept.  19,  and  Oct.  31,  1903;  abstract  in  M.  & 
S.  P.,  May  30,  1903,  1  p. 

Solvent  power  of  various  cyanide  solutions.  Proc.  Ch.  &  Met.  Soc.,  S.  A., 
vol.  1,  1897,  8  pp. 

DAVIS,  W.  H.     Care  of  cyanide  solutions.     Eng.  &  Min.  Jour.,  July  21, 

1904,  1  p. 

DIXON,  W.  A.  Note  on  so-called  "selective  action"  of  cyanide  for  gold. 
Inst.  Min.  &  Met.,  vol.  6,  1897,  6  pp. 

EKELEY  (J.  B.)  and  TATUM  (A.  L.).  Electrochemistry  of  solution  of  gold 
in  cyanide.  Elec.  &  Met.  Ind.,  Apr.,  1909,  1  p. ;  abstract  from  West.  Ch.  & 
Met. 

EYE,  C.  M.  Lead  acetate  in  cyanidation.  M.  &  S.  P.,  Jan.  9,  1909. 
"More  Recent  Cyanide  Practice,"  p.  246. 

HAMILTON,  E.  M.  Lead  acetate  in  the  cyanidation  of  silver  ores.  Mex. 
Min.  Jour.,  Aug.,  1910,  1  p. 

HOBSON,  F.  J.  Cyanidation  in  Mexico.  (Chemistry  with  some  history.) 
M.  &  S.  P.,  Aug.  1  and  8,  1908,  4  pp.  "More  Recent  Cyanide  Practice," 
p.  167. 

HOLT,  T.  P.  Chemical  advances  in  silver  cyaniding.  Salt  Lake  Min.  Rev., 
Jan.  15,  1910,  1  p. 

Cyanidation  of  silver  ores.  (Chemistry.)  M.  &  S.  P.,  Apr.  17,  2  pp.,  and 
July  31,  1909,  3  pp.  "More  Recent  Cyanide  Practice, "  pp.  186  and  282. 

HUNT,  B.  Cyanidation  in  Mexico.  (Chemistry.)  M.  &  S.  P.,  Aug.  29, 
1908,  1  p.  "  More  Recent  Cyanide  Practice, "  p.  176. 

Recovery  of  cyanide.  (By  precipitating  zinc  as  a  sulphate.)  M.  &  S.  P., 
May  4,  1901. 

JULIAN,  H.  F.    Losses  in  Cyanidation.    Min.  Mag.,  Oct.,  1911. 

LOEVY,  J.  Notes  on  action  of  alkaline  sulphides  in  solutions.  Proc.  Ch. 
&  Met.  Soc.,  S.  A.,  vol.  1,  1895,  5  pp. 

LOWDEN,  H.  B.  Phase  rule  in  cyanidation.  Met.  &  Chem.  Eng.,  July, 
1911,  1  p. 

LUNGWITZ,  E.  E.  Lixiviation  of  gold  deposits  by  vegetation.  Eng.  &  Min. 
Jour.,  vol.  69,  p.  500,  1  p. 


220          TEXT  BOOK  OF  CYANIDE  PRACTICE 

McCAUGHEY,  W.  J.  Solvent  effect  of  ferric  and  cupric  salt  solutions  upon 
gold.  Jour.  Am.  Ch.  Soc.,  Dec.,  1909,  10  pp. 

MACTEAR,  J.  On  "selective  action"  of  very  dilute  solutions  of  cyanide. 
Inst.  Min.  &  Met.,  vol.  4,  1895,  12  pp. 

Mora  (J.)  and  GRAY  (J.).  Destruction  of  cyanide.  Jour.  Ch.,  Met.,  & 
Min.  Soc.,  S.  A.,  Oct.,  1910,  8  pp. 

MOSHER,  D.  Chlorine  in  cyanidation  of  silver  ores.  Pac.  Miner,  May, 
1910,  1  p. 

Clancey  process.  Pac.  Miner,  Mar.,  1911;  Eng.  &  Min.  Jour.,  Apr.  1,  1911; 
Min.  World,  Feb.  11  and  Mar.  25,  1911;  M.  &  S.  P.,  Mar.  25,  1911. 

Cyanidation  of  silver  ores.     M.  &  S.  P.,  May  15,  1909,  3  pp. 

ORR,  W.  Regeneration  of  cyanide  solutions.  M.  &  S.  P.,  June  20, 
1903. 

PARKS,  J.  Notes  on  action  of  cyanogen  on  gold.  Inst.  Min.  &  Met., 
vol.  6,  1897,  1N0  pp. 

PLUNKETT,  T.  H.  Rate  of  solution  of  gold  in  cyanide.  Jour.  Can.  Min. 
Inst.,  vol.  7,  p.  192,  6  pp. 

SCHNEIDER,  E.  A.  Contributions  to  chemistry  of  cyanide  process.  Eng. 
&  Min.  Jour.,  vol.  60,  pp.  489  and  514,  2  pp. 

SEAMON,  W.  H.  Chemistry  of  cyanide  process.  Mex.  Min.  Jour.,  Aug., 
1910,  1  p. 

SHARWOOD,  W.  J.  Analysis  of  (four)  cyanide  mill  solutions.  Eng.  &  Min. 
Jour.,  Aug.  20,  1898,  1  p. 

Cyanidation  of  silver  ores.  (Chemistry.)  M.  &  S.  P.,  Sept.  26,  1908, 
3  pp.  "More  Recent  Cyanide  Practice, "  p.  178. 

Double  cyanides  of  zinc  with  potassium  and  with  sodium.  Eng.  &  Min. 
Jour.,  May  26,  1904. 

Notes  on  action  of  potassium  zinc  cyanide  solutions  on  gold.  Eng.  &  Min. 
Jour.,  Oct.  2,  1897,  1  p.;  Oct.  9,  1897,  1  p.;  Oct.  16,  1897,  2  pp. 

SIMPSON,  D.  Two  deterrents  (lime  and  oil)  to  the  dissolution  of  free  gold 
in  cyanide  process.  Inst.  Min.  &  Met.,  vol.  17,  1908,  1  p.;  abstract  in  Eng.  & 
Min.  Jour.,  Oct.  10,  1908. 

STUART,  J.  B.  Theory  of  dissolution  of  metals  by  cyanide.  M.  &  S.  P., 
Aug.  6,  1910,  2  pp. 

SULMAN,  H.  L.  Notes  on  behavior  of  haloid  elements  in  conjunction  with 
cyanide  process.  Proc.  Ch.  &  Met.  Soc.,  S.  A.,  vol.  1,  1895,  14  pp. 

TIPPETT,  J.  M.  Effect  on  solubility  of  gold  when  ore  is  crushed  between 
iron  surfaces.  Met.  &  Ch.  Eng.,  Sept.,  1910,  1  p. 

VON  OETTINGEN,  A.  Theory  of  solutions.  Proc.  Ch.  &  Met.  Soc.,  S.  A., 
vol.  2,  1899,  10  pp. 

WARWICK,  A.  W.  Notes  on  the  Clancy  process  and  its  operation.  Min. 
World,  Feb.  4,  1911,  1  p. 

Rate  of  solution  of  gold  in  cyanide  solutions.  Eng.  &  Min.  Jour.,  June  29, 
1895,  2  pp. 

Regeneration  of  cyanide  solutions.     Min.  Sci.,  Feb.  9,  1911,  1  p. 

WELLS,  J.  S.  C.  Is  zinc  potassium  cyanide  a  solvent  for  gold?  Eng.  & 
Min.  Jour.,  Dec.  21,  1895,  1  p. 

WHEELOCK,  R.  P.     Tests  on  acid  regeneration  of  copper  cyanide  solutions. 


CLASSIFIED   BIBLIOGRAPHY  221 

M.  &  S.  P.,  Dec.  18,  1909,  5  pp.;  Mar.  12,  1910,  1  p.     "More  Recent  Cyanide 
Practice, "  pp.  341  and  352. 

WHITE,  H.  A.  Solubility  of  gold  in  thiosulphates  and  thiocyanates.  Jour. 
Ch.,  Met.,  &  Min.  Soc.,  S.  A.,  Oct.,  1905,  3  pp.;  Dec.,  1905,  1  p.;  Jan.,  1906, 
1  p.;  Mar.,  1906,  1  p. 

ZACHERT,  V.  Electrolytic  difficulties  in  Clancy  process.  Min.  &  Met.  Jour., 
Sept.,  1911,  2  pp;  Min..  &  Eng.  World,  Nov.  4,  1911,  2  pp. 

Engineering  and  Mining  Journal.  Care  of  cyanide  solutions.  Vol.  78, 
p.  103. 

Clancy  process  of  ore  treatment.     Dec.  24,  1910,  1  p. 
New  Clancy  cyanide  patents.     Oct.  8,  1910,  3  pp. 
Cyanogen.     Mar.  16,  1905. 

Mexican  Mining  Journal.     Clancy  process.     Sept.,  1910,  1  p. 

Mining  World.  New  Clancy  method  of  ore  treatment.  Oct.  15,  1910, 
3pp. 

Pacific  Miner.  Clancy  process.  Nov.,  1909,  1  p.;  May,  1910;  Oct.,  1910, 
4pp. 

D.    Aeration  and  Oxidation 

ALDRICH,  T.  H.  Electrolytic  oxygen  in  cyanide  solutions.  Min.  &  Eng. 
World,  Oct.  21,  1911,  2  pp. 

BANKS,  J.  H.  G.  Upward  leaching  of  sand.  Eng.  &  Min.  Jour.,  July  22, 
1911,  1  p. 

CROSSE,  A.  F.  Assisting  the  solution  of  gold  in  cyanide  process  by  com- 
pressed air.  Jour.  Ch.,  Met.,  &  Min.  Soc.,  S.  A.,  Aug.,  1907,  1  p. 

DEANE,  A.  J.    Aeration  of  sand  charges.    Eng.  &  Min.  Jour.,  July  29,  1911. 

DURANT,  H.  T.  Application  of  oxygen  in  cyanide  process.  Proc.  Ch.  & 
Met.  Soc.,  S.  A.,  vol.  2,  1897,  5  pp. 

GROPELLO,  E.  F.  Dorcas  pneumatic  cyanide  mill.  M.  &  S.  P.,  May  11, 
1901,  1  p. 

GROTHE,  A.    Use  of .  compressed  air  in  cyanidation.     Min.  World,  Jan.  11, 

1908,  1  p. 

HUBBARD,  J.  D.  Cyaniding  concentrate  at  Taracol,  Korea.  (Includes 
aeration.)  M.  &  S.  P.,  Oct.  2,  1909,  2  pp.  "  More  Recent  Cyanide  Practice, " 
p.  318. 

JAMES,  G.  A.  Preliminary  treatment  of  water  and  air  in  cyanide  process. 
M.  &  S.  P.,  Sept.  30,  1911. 

JULIAN,  H.  F.  Action  of  oxygen  in  cyanide  solutions.  M.  &  S.  P.,  Oct.  27, 
1906,  1  p.  "Recent  Cyanide  Practice,"  p.  155.  Abstract  from  Jour.  Ch., 
Met.,  &  Min.  Soc.,  S.  A. 

How  oxygen  assists  and  retards  the  dissolution  of  gold  in  cyanide.  M.  & 
S.  P.,  Dec.  30,  1905,  1  p. 

MEGRAW,  H.  A.    Oxidation  and  cyanidation.    Eng.  &  Min.  Jour.,  Oct.  2, 

1909,  2  pp. 

MOSHER,  D.  Ozone  in  treatment  of  silver  ores  in  cyaniding.  Pac.  Miner, 
Sept.,  1909,  4  pp. 

OHLY,  J.  Pneumatic  process  for  leaching  and  cyaniding.  M.  &  S.  P., 
Apr.  27,  1901,  1  p. 


222          TEXT  BOOK  OF  CYANIDE  PRACTICE 

TAYS,  E.  A.  H.  Cyanide  notes  on  leaching  and  aeration.  M.  &  S.  P., 
Sept.  1,  1906,  2  pp. 

TERRY,  J.  T.  Oxidizing  agents  in  cyanide  mill  solutions.  M.  &  S.  P., 
Aug.  30,  1902. 

Mining  and  Scientific  Press.  Barium  dioxide.  (Results  of  use  in  cyanid- 
ing.)  M.  &  S.  P.,  Nov.  15,  1902. 

Begeer  cyanide  process.     (Aeration  of  solution.)     May  31,  1902. 

E.    Commercial  Cyanide  and  its  Analysis 

ALLEN,  A.  H.  Manufacture  and  impurities  of  commercial  cyanide.  Eng. 
&  Min.  Jour.,  vol.  76,  p.  239,  1  p.,  p.  241. 

BELL,  RALSTON.  Commercial  cyanide.  (Concerning  estimation.)  Eng. 
&  Min.  Jour.,  July  30,  1910,  1  p. 

Rapid  analysis  of  commercial  cyanide.  Eng.  &  Min.  Jour.,  May  28,  1910, 
2pp. 

Spurious  potassium  cyanide.     Eng.  &  Min.  Jour.,  May  21,  1910,  1  p. 

BETTEL,  WM.  Fixture  of  atmospheric  nitrogen  in  cyanide  manufacture. 
S.  A.  Min.  Jour.,  Aug.  7,  1909,  1  p. 

CLENNELL,  J.  E.  Commercial  potassium  cyanide.  Eng.  &  Min.  Jour., 
June  25,  1910,  1  p. 

Methods  of  determining  potassium  in  sodium  cyanide.  Eng.  &  Min.  Jour., 
June  25,  1910,  1  p. 

Spurious  potassium  cyanide.     Eng.  &  Min.  Jour.,  Jan.  15,  1910,  1  p. 

DOVETON  (G.)  et  al.  Impurities  in  commercial  cyanide.  Eng.  &  Min. 
Jour.,  Mar.  28,  Apr.  4,  Apr.  11,  May  2,  and  Aug.  15,  1903. 

DURANT,  H.  T.  Notes  on  commercial  cyanide.  Eng.  &  Min.  Jour.,  Aug. 
18,  1906,  1  p. 

EWAN,  T.  Estimation  of  sulphide  in  alkali  cyanide.  Jour.  Soc.  Ch.  Ind., 
Jan.  15,  1909,  3  pp. 

FELDTMAN  (W.  R.)  and  BETTEL  (WM.).  Notes  on  estimation  of  sulphides 
and  cyanates  in  commercial  cyanide.  Proc.  Ch.  &  Met.  Soc.,  S.  A.,  vol.  1, 
1896,  9  pp. 

HAMILTON,  E.  M.  Spurious  potassium  cyanide.  Eng.  &  Min.  Jour., 
Feb.  12,  1910,  1  p. 

HOLBROOK,  E.  A.     Sodium  cyanide.     (Undesirable.)    M.  &  S.  P.,  May  16, 

1908.  "More  Recent  Cyanide  Practice,"  p.  142. 

LAWRIE,  R.  B!  Use  of  cyanide  of  sodium.  M.  &  S.  P.,  May  7,  1904, 
lp. 

LOEVY,  J.  Estimation  of  sulphides  in  cyanides.  Proc.  Ch.  &  Met.  Soc., 
S.  A.,  vol.  2,  1899,  3  pp. 

MAGENAU,  W.  Negative  experience  with  sodium  cyanide.  Eng.  &  Min. 
Jour.,  Aug.  25,  1906. 

MOORE,  T.  W.  Composition  of  commercial  cyanide  of  potassium.  Jour. 
Soc.  Ch.  Ind.,  Mar.  31,  1902. 

OLDFIELD,  F.  W.     Commercial  cyanide.     Eng.  &  Min.  Jour.,  May  2,  1903. 

Ross,  F.  A.     Spurious  potassium  cyanide.     Eng.  &  Min.  Jour.,  Oct.  23, 

1909,  and  Apr.  2,  1910. 


CLASSIFIED  BIBLIOGRAPHY  223 

SEAMON,  W.  H.  Analysis  of  commercial  cyanide.  In  "A  Manual  for 
Assayers  and  Chemists,"  1910. 

SHARWOOD,  W.  J.  Commercial  sodium  and  potassium  cyanide.  (Includ- 
ing bibliography.)  Eng.  &  Min.  Jour.,  Mar.  19,  1910,  3  pp. 

SNODGRASS,  J.     Manufacture  of  cyanide.    S.  A.  Mines,  Aug.  31,  1907,  1  p. 

STAYER,  W.  H.     Strength  of  cyanide.     Eng.  &  Min.  Jour.,  Sept.  16,  1905. 

WHITBY,  W.  A.  Noles  on  commercial  cyanide  of  potassium.  (With 
determinations.)  Proc.  Ch.  &  Met.  Soc.,  S.  A.,  vol.  3,  1902-1903,  7  pp.; 
abstract  in  Eng.  &  Min.  Jour.,  Feb.  28,  1903,  1  p. 

Engineering  and  Mining  Journal.     Sodium  cyanide.     July  14,  1904. 
The  two  cyanides.     June  29,  1905. 

Mining  and  Scientific  Press.  Sodium  cyanide  in  practice.  Aug.  5  and 
Sept.  16,  1905. 

F.     Analytical  Chemistry  of  Cyanide  Solution 

AD  AIR,  A.  Estimation  of  cyanide.  Eng.  &  Min.  Jour.,  Apr.  11,  1903; 
abstract  from  Jour.  Ch.,  Met.,  &  Min.  Soc.,  S.  A. 

ALLEN,  A.  W.  Titrating  cyanide- solution  in  presence  of  silver.  M.  &  S.  P., 
JulyS,  1911. 

BAILAR,  J.  C.  Potassium  cyanide  and  silver  nitrate.  (Titration.)  Min. 
World,  Aug.  13,  1910. 

BELL,  R.  Protective  alkalinity  in  cyanide  solutions.  Eng.  &  Min.  Jour., 
July  2,  1910,  1  p. 

BETTEL,  WM.  Estimation  of  oxygen  in  working  cyanide  solution.  Proc. 
Ch.  &  Met.  Soc.,  S.  A.,  1896,  vol.  1,  5  pp. 

Technical  analysis  of  working  cyanide  solutions.  Proc.  Ch.  &  Met.  Soc., 
S.  A.,  vol.  1,  1895,  8  pp. 

BROWNE,  R.  S.  Estimation  of  efficiency  of  solutions.  Pac.  Miner,  May, 
1910. 

BROWNING  (P.  E.)  and  PALMER  (H.  E.).  Method  for  qualitative  separation 
and  detection  of  ferrocyanides,  ferricyanides,  and  sulphocyanides.  Am. 
Jour.  Sci.,  June,  1907,  3  pp. 

BULLOCK,  L.  N.  B.  Cyanide  practice  at  Copala.  (Estimation  of  pro- 
tective alkalinity.)  M.  &  S.  P.,  June  8  and  Nov.  23,  1907,  Jan.  11, 
1908. 

BURGGRAF,  J.  Notes  on  normal  acid  and  alkali  solutions.  Mex.  Min. 
Jour.,  Aug.,  1910. 

CLENNELL,  J.  E.  Analytical  work  in  connection  with  cyanide  process. 
Trans.  Inst,  Min.  &  Met.,  vol.  12,  1903,  24  pp.;  abstract  in  Eng.  &  Min.  Jour., 
June  27,  1903,  1  p. 

Cyanide  solution  test  at  Creston-Colorado  plant.  Mex.  Min.  Jour.,  Aug., 
1910,  2  pp. 

Estimation  of  available  cyanide.     Eng.  &  Min.  Jour.,  Mar.  31,  1904,  1  p. 

Estimation  of  chief  constituents  in  cyanide  solutions.  Eng.  &  Min.  Jour., 
June  29,  1905,  2  pp. 

Estimation  of  cyanide  in  cyanide  solutions.  Eng.  &  Min.  Jour.,  July  4, 
1903,  1  p.;  abstract  from  Inst.  Min.  &  Met.,  vol.  12,  1903. 


224          TEXT  BOOK  OF  CYANIDE  PRACTICE 

Estimation  of  cyanogen  in  impure  solutions.  Eng.  &  Min.  Jour.,  June  22, 
1895,  2  pp. 

Examination  of  various  methods  for  estimation  of  ferrocyanides.  Eng.  & 
Min.  Jour.,  Nov.  7,  1903,  3  pp. 

Manganese  in  cyanide  solutions.  (Detection,  estimation,  etc.)  Eng.  & 
Min.  Jour.,  Nov.  24,  1904. 

Notes  on  analysis  of  cyanide  solutions.  Proc.  Ch.  &  Met.  Soc.,  S.  A., 
vol.  1,  1895,  7  pp. 

COLLINGRIDGE,  B.  Errors  due  to  presence  of  potassium  iodide  in  testing 
cyanide  solutions  for  protective  alkalinity.  Inst.  Min.  &  Met.,  Jan.  20,  1910, 
3pp. 

CRANE,  W.  R.  Bibliography  of  chemical  analysis  in  cyaniding.  In  "Index 
of  Mining  Engineering  Literature,"  1  p. 

CROSSE,  A.  F.  Analysis  of  cyanide  solutions.  Proc.  Ch.  &  Met.  Soc., 
S.  A.,  vol.  3,  1902,  12  pp. 

Estimation  of  oxygen  in  working  cyanide  solutions.  Proc.  Ch.  &  Met. 
Soc.,  S.  A.,  vol.  2,  1898,  14  pp. 

Estimation  of  protective  alkali  in  cyanide  solutions.  Proc.  Ch.  &  Met. 
Soc.,  S.  A.,  vol.  2,  1899,  7  pp. 

DEL  MAR  (A.)  et  al.  Estimation  of  cyanide  in  mill  solutions.  M.  &  S.  P., 
Jan.  15,  Mar.  26,  and  Apr.  16,  1910. 

.     GREEN,  L.  M.     Estimation  of  sulpho-  and  ferricyanides,  etc.,  in  cyanide 
solutions  containing  copper.     Inst.  Min.  &  Met.,  vol.  18,  1908,  7  pp. 

Method  of  testing  cyanide  solutions  containing  zinc.  Inst.  Min.  &  Met., 
vol.  10,  1901,  12  pp. 

Use  of  mercuric  chloride  in  testing  cyanide  solutions.  M.  &  S.  P.,  Jan.  28, 
1905. 

HAMILTON,  E.  M.  Silver  in  sulphocyanide  determinations.  M.  &  S.  P., 
Mar.  11,  1911,  1  p. 

JAY,  C.  H.  Duties  of  cyanide  chemist.  Eng.  &  Min.  Jour.,  Oct.  17,  1908, 
1  p.;  abstract  from  West.  Ch.  &  Met. 

Laboratory  methods  used  in  modern  cyanide  mills.  West.  Ch.  &  Met., 
May,  1908,  8  pp. 

Some  laboratory  methods  in  use  at  cyanide  plant  of  Golden  Sunlight  and 
Ohio  mining  properties.  West.  Ch.  &  Met.,  Sept.,  1906,  3  pp. 

PRISTER,  A.  Industrial  method  for  determination  of  oxygen  in  working 
cyanide  solutions.  Jour.  Ch.,  Met.,  &  Min.  Soc.,  S.  A.,  Apr.,  1904,  5  pp.; 
May,  1904. 

SHARWOOD,  W.  J.  Analysis  of  (four)  cyanide  mill  solutions.  Eng.  &  Min. 
Jour.,  Aug.  20,  1898,  1  p. 

Estimation  of  cyanide  effluents.  (Protective  alkalinity.)  Eng.  &  Min. 
Jour.,  Aug.  8,  1908;  abstract  from  Jour.  Ch.,  Met.,  &  Min.  Soc.,  S.  A. 

Estimation  of  cyanogen.     Jour.  Am.  Ch.  Soc.,  May,  1897. 

TREADWELL,  W.  D.  Titration  of  potassium  cyanide  in  presence  of  potas- 
sium ferrocyanide.  M.  &  S.  P.,  Nov.  11,  1911. 

VAN  OSDEL,  E.  R.  Alkaline  zinc  titration.  Eng.  &  Min.  Jour.,  vol.  82, 
p.  1110. 

WILLIAMS,  G.  W,      Determination   of    (chemical)    constants  in"  working 


CLASSIFIED   BIBLIOGRAPHY  225 

cyanide  solutions.     Jour.  Ch.,  Met.,  &  Min.  Soc.,  S.  A.,  Feb.,  1904,  12  pp.; 
May,  1904,  7  pp. 

Mining  and  Scientific  Press.  Crosse's  method  of  determining  oxygen  in 
cyanide  solutions.  May  3,  1902. 

G.  Assaying,  Samplers,  and  Sampling 

ARENTS,  A.  Test  for  precious  metals  in  cyanide  solutions.  T.  A.  I.  M.  E., 
vol.  34,  1903,  1  p.;  abstract  in  Eng.  &  Min.  Jour.,  Mar.  21,  1903;  abstract  in 
M.  &  S.  P.,  Apr.  18,  1903. 

BARTON,  W.  H.  Assay  scheme  for  cyanide  solutions.  (Chiddy  method.) 
West.  Ch.  &  Met.,  Feb.,  1908,  1  p.;  abstract  in  Eng.  &  Min.  Jour.,  Aug.  8, 
1908. 

BETTEL,  WM.  Estimating  gold  in  cyanide  solutions.  Min.  World,  July 
16,  1910,  1  p.;  abstract  from  S.  A.  Min.  Jour. 

Colorimetric  estimation  of  gold  in  cyanide  solutions.  Min.  &  Eng.  World, 
Nov.  11,  1911;  abstract  from  S.  A.  Min.  Jour. 

BIRD,  F.  A.  Assay  of  cyanide  precipitate.  M.  &  S.  P.,  Oct.  9,  1909,  1  p. 
"More  Recent  Cyanide  Practice,"  p.  326. 

BROWN,  R.  G.  Some  tailing  samplers.  M.  &  S.  P.,  Nov.  3,  1906,  2  pp. 
"Recent  Cyanide  Practice,"  p.  157. 

CARTER,  T.  L.  Notes  for  assaying  cyanide  solutions  for  gold.  Eng.  & 
Min.  Jour.,  Nov.  15,  1902. 

CASSEL,  H.  R.  Colorimetric  estimation  of  gold  in  cyanide  solutions. 
Eng.  &  Min.  Jour.,  Oct.  31,  1903,  1  p. 

CHIDDY,  A.     Assay  of  cyanide  solutions.     Eng.  &  Min.  Jour.,  Mar.  28,  1903. 

DODS,  R.     Sampling.     Aust.  Min.  &  Eng.  Rev.,  Oct.  5,  1909,  3  pp. 

FULTON  (C.  H.)  and  CRAWFORD  (C.  H.).  Notes  on  assay  of  zinc  precipitate. 
Bull.  No.  5,  S.  Dak.  Sch.  of  Mines,  Feb.,  1902,  10  pp. 

HENDERSON,  A.  M.  Assaying  cyanide  solutions.  Eng.  & .  Min.  Jour., 
Aug.  5,  1905. 

HOLT,  T.  P.  Assay  of  gold-silver  cyanide  solutions.  (Modification  of 
Chiddy  method.)  M.  &  S.  P.,  June  11,  1910,  1  p.  "More  Recent  Cyanide 
Practice,"  p.  403. 

HOOD,  D.  N.  Testing  filter  press  tail  solutions.  (For  assay.)  Eng.  & 
Min.  Jour.,  Jan.  21,  1911. 

GRAUER,  R.  Assay  of  cyanide  solutions.  Eng.  &  Min.  Jour.,  Dec.  5, 
1903. 

LINDEMAN,  M.  Assay  of  cyanide  solutions.  Eng.  &  Min.  Jour.,  July  7, 
1904. 

LODGE,  R.  W.  Assay  of  zinc-box  precipitate.  T.  A.  I.  M.  E.,  vol.  34, 
1903,  19  pp.  See  "Notes  on  Assajdng"  by  Lodge. 

MACFARREN,  H.  W.  Sand-tank  sampler.  M.  &  S.  P.,  Nov.  30,  1907,  and 
Nov.  7,  1908. 

McMiLLEN,  D.  A.  An  auto-hydraulic  sampling  device.  Eng.  &  Min. 
Jour.,  Nov.  19,  1910,  1  p. 

MAGENAU,  W.  Assay  of  cyanide  solutions.  (Various  typical  methods.) 
M.  &  S.  P.,  Apr.  14,  1906,  3  pp.  "Recent  Cyanide  Practice,"  p.  42. 


226          TEXT  BOOK  OF  CYANIDE  PRACTICE 

MARTEL,  J.  L.  Assay  of  cyanide  solutions.  West.  Ch.  &  Met.,  Apr., 
1907,  1  p. 

MILLER,  G.  D.  Assay  of  cyanide  solutions.  Eng.  &  Min.  Jour.,  June  23, 
1904. 

MOIR,  J.  New  and  rapid  method  of  detecting  and  estimating  gold  in 
working  cyanide  solutions.  Jour.  Ch.,  Met.,  &  Min.  Soc.,  S.  A.,  Sept.,  1903, 
2  pp.;  Mar.,  1904,  3  pp.;  abstract  in  M.  &  S.  P.,  Nov.  28,  1903,  1  p. 

MONAHAN,  F.  W.  Device  for  sampling  zinc-box  solutions.  Eng.  &  Min. 
Jour.,  Mar.  12,  1910. 

PEAD,  C.  H.  Automatic  sampler  for  tailings,  sands,  and  slimes.  Proc. 
Ch.  &  Met.  Soc.,  S.  A.,  vol.  3,  1903,  2  pp.;  abstract  in  M.  &  S.  P.,  June  17, 

1903,  1  p. 

PICKETT,  T.  L.  Lead  tray  method  of  assaying  cyanide  solutions.  Pac. 
Miner,  May,  1910,  1  p. 

PRISTER,  A.  Colorimetric  method  for  determination  of  gold  in  cyanide 
solutions.  Jour.  Ch.,  Met.,  &  Min.  Soc.,  S.  A.,  Dec.,  1903,  2  pp.;  abstract 
in  Eng.  &  Min.  Jour.,  Feb.  25,  1904,  1  p. 

Purple  of  Cassius  test  for  use  in  cyanide  works.  Jour.  Ch.,  Met.,  &  Min. 
Soc.,  S.  A.,  June,  1904. 

SEAMON,  W.  H.  Methods  for  assaying  in  cyanide  plants.  West.  Ch.  & 
Met.,  Aug.,  1909,  4  pp.;  abstract  in  Eng.  &  Min.  Jour.,  Sept.  25,  1909.  See 
"A  Manual  for  Assayers  and  Chemists"  by  Seamon. 

SIMPSON,  D.     Sand  sampling  in  cyanide  works.     Inst.  Min.  &  Met.,  vol.  16, 

1906,  12  pp. 

Engineering  &  Mining  Journal.    Filter  for  slime  samples.     Nov.  11,  1911. 

Mining  World.     Automatic  tailing  samplers.     July  30,  1910,  1  p. 

Mining  and  Scientific  Press.  Assay  of  cyanide  solution.  R.  S.  Browne, 
Apr.  11,  1903;  H.  W.  Gender,  Mar.  30,  1907;  A.  H.  Jones,  May  16,  1903; 
A.  MacDonald,  June  8,  1907;  D.  Muir,  May  4,  1907;  W.  F.  Tindall,  June  8, 
1907;  N.  C.  Stines,  Apr.  28,  1906.  Gender,  MacDonald,  Muir,  and  Stines  in 
"Recent  Cyanide  Practice." 

H.   Ore  Testing  and  Physical  Tests 

ALDERSON,    M.   W.     Laboratory   cyanide   tests.     Min.    World,    Feb.    16, 

1907,  2  pp. 

ALLAN,  J.  F.  Notes  on  preliminary  tests  of  cyanide  treatment  of  silver 
ores  in  Mexico.  T.  A.  I.  M.  E.,  1904,  vol.  35,  19  pp. 

BEGEER,  B.  W.  Laboratory  agitation  apparatus.  M.  &  S.  P.,  Dec.  17, 
1910. 

BROWNE,  R.  S.     Testing  ores  for  cyanide  treatment.     M.  &  S.  P.,  Jan.  2, 

1904,  1  p.;  Jan.  9,  1  p.;  Jan.  16,  1  p. 

BUSKETT,  E.  W.  Tube  mill  for  the  laboratory.  Eng.  &  Min.  Jour.,  Sept. 
16,  1911. 

CLENNELL,  J.  E.  Notes  on  experimental  metallurgy.  Proc.  Ch.  &  Met. 
Soc.,  S.  A.,  vol.  2, 1898, 10  pp. ;  abstract  in  M.  &  S.  P.,  Feb.  18  and  25,  1899, 2  pp. 

CLEVENGER,  G.  H.  Agitator  for  cyanide  tests.  M.  &  S.  P.,  May  29, 
1909,  1  p,  "More  Recent  Cyanide  Practice,"  p.  278. 


CLASSIFIED  BIBLIOGRAPHY  227 

DENNY,  H.  S.  Grading  analyses.  Eng.  &  Min.  Jour.,  Mar.  9,  1905,  1  p.; 
M.  &  S.  P.,  Mar.  25,  and  Apr.  1,  1905,  2  pp.;  abstract  from  S.  A.  Ass.  of  Engrs. 

FURMAN,  H.  VAN  F.  Laboratory  tests  in  connection  with  extraction  of 
gold  from  ores  by  cyanide  process.  T.  A.  I.  M.  E.,  vol.  26,  1896,  13  pp.; 
abstract  in  M.  &  S.  P.,  Nov.  7  to  Dec.  5,  1896.  See  "A  Manual  of  Practical 
Assaying"  by  Furman.  ^ 

GAYFORD,  E.     Mill  tests.     M.  &  S.  P.,  May  16,  1908. 

Ore  testing  at  Salt  Lake  City.     M.  &  S.  P.,  Jan.  25,  1908,  3  pp. 

GLOVER,  A.  L.  Simple  laboratory  agitator.  Eng.  &  Min.  Jour.,  Aug.  5, 
1911. 

HALLETT,  S.  I.  Treatment  of  oxidized  silver-lead  ores  of  Aspen,  Colo.,  in 
laboratory  by  cyanide.  M.  &  S.  P.,  May  2,  1903,  1  p. 

HYDER,  F.  B.  Estimation  of  pulp  from  its  specific  gravity.  Proc.  Colo. 
Sci.  Soc.,  Nov.,  1910,  7  pp.;  abstract  in  Mines  &  Mins.,  July,  1911,  2  pp. 

LAMB,  M.  R.  Rapid  estimation  of  pulp  in  cyanide  tanks.  Eng.  &  Min. 
Jour.,  Jan.  15,  1910,  1  p. 

LAWLOR,  T.  S.  Brown  type  of  laboratory  agitator.  M.  &  S.  P.,  Aug.  7, 
1909,  1  p.  "More  Recent  Cyanide  Practice, "  p.  290. 

MERRILL,  C.  W.  MacArthur-Forrest  process.  Experiments  in  the  met- 
allurgical laboratory.  M.  &  S.  P.,  Apr.  23,  1892,  1  p. 

NUTTER,  E.  H.  Simple  solution  meter.  M.  &  S.  P.,  Dec.  1,  1906,  1  p. 
"Recent  Cyanide  Practice,"  p.  170. 

RIEBLING,  H.  F.  A.  Notes  on  preliminary  cyanide  work.  (Laboratory 
testing.)  West.  Ch.  &  Met.,  Oct.,  1907,  5  pp. 

Recommending  the  cyanide  process.  (Concerning  laboratory  tests.) 
Min.  Reptr.,  Feb.  28,  1907,  1  p. 

ROBERTSON,  J.  J.  Cyanide  tests  on  Temiskaming  ores.  Jour.  Can.  Min. 
Inst.,  vol.  9,  p.  396,  6  pp. 

SHARWOOD,  W.  J.  Measurement  of  pulp  and  tailing.  Min.  Mag.,  Nov., 
1909,  to  Jan.,  1910,  23  pp.  Reprinted  in  pamphlet  form. 

SIMMONDS,  E.  H.  Laboratory  investigation  of  ore.  Pac.  Miner,  Oct., 
1909,  2  pp. 

Place  and  value  of  small  scale  ore  tests.  M.  &  S.  P.,  Apr.  22  and  29,  1905, 
2  pp.;  abstract  from  Trans.  Cal.  Miners'  Assn. 

SIMPSON,  D.  I.  R.  New  method  of  obtaining  density  of  settled  sand. 
Jour.  Ch.,  Met.,  &  Min.  Soc.,  S.  A.,  Dec.,  1906,  1  p. 

SPAULDING,  C.  F.  Measuring  spacific  gravity  in  agitators.  M.  &  S.  P., 
Sept.  16,  1911. 

STABLER,  H.  Grading  analyse  -.d  their  application.  Bull.  Inst.  Min. 
&  Met.,  May  19,  1910,  14  pp. 

Grading  analyses  and  their  application.  Jour.  Ch.,  Met.,  &  Min.  Soc.,  S.  A., 
May,  1910,  7  pp.;  Dec.,  1910,  7  pp. 

STEINEN,  C.    Solution  meter.    Eng.  &  Min.  Jour.,  Oct.  7,  1911. 

TOOMBS,  C.  Screen  assay  on  Meyer  and  Charlton  under  "the  new  metal- 
lurgy." Jour.  Ch.,  Met.,  &  Min.  Soc.,  S.  A.,  Mar.,  1907,  2  pp.;  May,  1907, 
2  pp.;  June,  1907,  3  pp.;  Aug.,  1907,  2  pp. 

YATES,  A.    Grading  assays  and  grinding  efficiencies.    Jour.  Ch.,  Met.,  & 


228          TEXT  BOOK  OF  CYANIDE  PRACTICE 

Min.  Soc.,  S.  A.,  Dec.,  1908,  3  pp.;  Jan.,  1909,  1  p.;  Apr.,  1909,  2  pp.;  May, 
1909,  1  p.;  abstract  in  M.  &  S.  P.,  May  1,  1909,  1  p". 

YOUNG,  G.  J.     Method  of  slime  testing.     Min.  Mag.,  Aug.,  1910,  1  p. 

Mining  and  Scientific  Press.  Bibliography  of  testing  ores  preliminary  to 
cyaniding.  M.  &  S.  P.,  Nov.  11,  1905. 

7.    Alkalinity  and  Lime 

BARNEY,  L.  W.  Rapid  estimation  of  available  calcium  oxide  in  lime  used 
in  cyanide  process.  Trans.  A.  I.  M.  E.,  Oct.,  1911.  Abstract  in  Eng.  &  Min. 
Jour.,  Nov.  18,  1911;  in  Min.  &  Eng.  World,  Nov.  4,  1911;  in  M.  &  S.  P., 
Oct.  14,  1911. 

BEALL,  R.  S.  Determination  of  causticity  of  lime.  West.  Ch.  &  Met., 
Oct.,  1905,  2  pp. 

BISHOP,  L.  D.  Notes  on  cyanidation.  (Lime  and  increased  temperature.) 
Electrochem.  &  Met.  Ind.,  Feb.,  1909,  2  pp.;  Eng.  &  Min.  Jour.,  Apr.  24,  1909, 
2  pp.;  Min.  World,  Mar.  13,  1909,  2  pp.;  abstract  from  Proc.  Colo.  Sci.  Soc. 

BULLOCK,  L.  N.  B.  Cyanide  practice  at  Copala,  Mexico.  (Increasing 
protective  alkalinity.)  M.  &  S.  P.,  June  8,  1907,  1  p.  "Recent  Cyanide 
Practice,"  p.  231. 

CROGHAN,  E.  H.  Notes  on  estimation  of  caustic  lime.  Jour.  Ch.,  Met., 
&  Min.  Soc.,  S.  A.,  Aug.,  1907,  to  Jan.,  1908,  20  pp. 

DEL  MAR,  A.  Precipitation  of  gold  by  lime.  Eng.  &  Min.  Jour.,  Jan.  15, 
1910. 

GARDNER,  B.  L.  Action  of  alkaline  solutions  in  cyaniding  weathered  py- 
ritic  tailing.  Jour.  W.  A.  Cham,  of  Mines,  Oct.  31,  1907,  4  pp. 

GAYFORD,  E.  Use  of  lime  as  an  alkaline  reagent  in  cyaniding.  M.  &  S.  P., 
Jan.  3,  1903,  1  p. 

GRAY,  J.  Influence  of  moist  air  on  quicklime.  Jour.  Ch.,  Met.,  &  Min. 
Soc.,  S.  A.,  May,  1909,  1  p. 

HOLT,  T.  P.     Lime  reactions  in  Cyaniding.     Mines  &  Mins.,  Mar.,  1911,  1  p. 

SHARWOOD,  W.  J.  Laboratory  tests  on  use  of  coarse  and  fine  lime  for 
cyaniding.  Jour.  Ch.,  Met.,  &  Min.  Soc.,  S.  A.,  Apr.,  1908,  5  pp.;  abstract 
in  Eng.  &  Min.  Jour.,  Aug.  8,  1908. 

SWEETLAND,  E.  G.  Use  of  alkalis  in  cyanide  process.  M.  &  S.  P.,  July 
25,  1903. 

WILLIAMS,  G.  W.  Notes  on  lime,  clean-up,  etc.  Jour.  Ch.,  Met.,  &  Min. 
Soc.,  S.  A.,  July  to  Sept.,  1905,  7  pp. 

Engineering  and  Mining  Journal.  Lime  and  caustic  soda  in  cyaniding. 
Vol.  82,  p.  771. 

J.     Classification,  Dewatering,  and  Settlement 

ALMETTE,  S.  Notes  on  classifiers.  (For  tube  mills.)  Min.  Sci.,  Dec.  30, 
1909,  1  p. 

ASHLEY,  H.  E.  Chemical  control  of  slime.  T.  A.  I.  M.  E.,  vol.  41,  1910, 
16pp. 

Colloid  matter  of  clay  and  its  measurement.  U.  S.  Geol.  Survey,  Bull. 
No.  388,  1909,  65  pp. 


CLASSIFIED   BIBLIOGRAPHY  229 

Theory  of  settlement  of  slime.     M.  &  S.  P.,  June  12  and  Aug.  28,  1909,  2  pp. 

AYTON,  E.  F.  Sand  and  slime  separation  at  Arianena  mill.  Pac.  Miner, 
Nov.,  1910,  2  pp. 

BAILDON,  S.  R.  Free  settlement  method  of  separating  slime.  M.  &  S.  P., 
Oct.  23,  1909,  1  p. 

BIGELOW,  D.  E.  Water  consumption  in  ore  treatment,  Kalgoorlie,  W.  A. 
M.  &  S.  P.,  Apr.  23,  1904. 

Boss,  M.  P.    Segregation  of  solids  in  liquids.     M.  &  S.  P.,  Sept.  9,  1911. 

BROOKS,  H.  J.  Sand  collecting.  M.  &  S.  P.,  Dec.  4,  1909.  "More 
Recent  Cyanide  Practice, "  p.  302. 

BROWN,  S.  E.  .  Conical-bottom  tanks.     M.  &  S.  P.,  Aug.  15,  1908. 

BROWNE,  R.  S.  Dewatering  appliances  for  sand  collecting  tanks.  Pac. 
Miner,  Oct.,  1909,  3  pp. 

CALDECOTT,  W.  A.  Colloidal  silicic  acid  in  slime.  Jour.  Ch.,  Met.,  & 
Min.  Soc.,  S.  A.,  Jan.,  1907,  1  p. 

Continuous  collection  of  sand  for  cyaniding.  M.  &  S.  P.,  Nov.  13,  1909, 
2  pp.  "More  Recent  Cyanide  Practice,"  p.  329.  Abstract  from  Jour.  Ch., 
Met.,  &  Min.  Soc.,  S.  A.,  Aug.,  1909,  11  pp. 

CARTER,  T.  L.  Notes  on  classification  for  cyanidation,  and  cyanide  treat- 
ment. Jour.  Ch.,  Met.,  &  Min.  Soc.,  S.  A.,  Sept.,  1903,  6  pp.;  Mar.  and  Apr., 
1904,  4  pp.;  abstract  in  M.  &  S.  P.,  Dec.  12  and  19,  1903,  2  pp. 

CHRISTENSEN,  A.  O.  Free  and  hindered  settling  of  mineral  grains.  Eng. 
&  Min.  Jour.,  Sept.  11,  1909,  6  pp. 

EAMES,  L.  B.  Percentage  of  moisture  vs.  specific  gravity.  Mex.  Min. 
Jour.,  Oct.,  1911. 

FORBES,  D.  L.  H.  Slime  thickening  at  El  Tigre,  Sonora.  Eng.  &  Min. 
Jour.,  Oct.  7,  1911,  2  pp. 

FREE,  E.  E.  Phenomena  of  flocculation  and  deflocculation.  Jour.  Frank- 
lin Institute,  June  and  July,  1910,  29  pp. 

FULTON,  C.  H.  Separation  of  sand  from  slime  in  cyanide  process.  (Home- 
stake  and  Hidden  Fortune  mills.)  Mines  &  Mins.,  Dec.,  1904. 

GARDNER,  B.  L.  Slime  settlement.  Min.  &  Eng.  World,  Nov.  11,  1911; 
Eng.  &  Min.  Jour.,  Sept.  2,  1911;  Min.  Mag.;  Aug.,  1911;  abstract  from  Jour. 
W.  A.  Cham.  Mines,  May,  1911. 

HAMILTON,  E.  M.  All-sliming.  (Sand  collection.)  M.  &  S.  P.,  Aug.  21, 
1909,  1  p.  "More  Recent  Cyanide  Practice,"  p.  293. 

HUNTLEY,  R.  E.  Slime  settler  or  dewaterer  at  Kalgoorlie.  Jour.  W.  A. 
Cham,  of  Mines,  July  30,  1910. 

JOHNSON,  E.  H.  Classification  of  tailing  pulp  prior  to  cyaniding.  Jour. 
Ch.,  Met.,  &  Mm.  Soc.,  S.  A.,  Oct.,  1910,  8  pp.;  Jan.  and  Feb.,  1911,  7  pp. 

Classification  of  tailing  pulp.     Min.  &  Eng.  World,  July  15,  1911,  1  p. 

JOHNSON,  J.  E.  Removal  of  sand  from  waste  water  in  ore  dressing  oper- 
ations. Eng.  &  Min.  Jour.,  Dec.  31,  1903,  1  p.  "  Notes  on  Metallurgical 
Mill  Construction. " 

NEAL,  W.  Diaphragm  classifying  cones  and  tube-milling.  M.  &  S.  P., 
Apr.  2,  1910,  3  pp.  "More  Recent  Cyanide  Practice,"  p.  389. 

NICHOLS,  H.  G.  Free  settlement  methods  of  separating  slime.  M.  &  S.  P., 
Sept.  11,  1909,  2  pp. 


230          TEXT  BOOK  OF  CYANIDE  PRACTICE 

Method  of  settling  slimes  as  applied  to  their  separation  from  solution  in 
cyanide  treatment.  Inst.  Min.  &  Met.,  vol.  17,  1908,  37  pp.;  abstract  in 
Eng.  &  Min.  Jour.,  Apr.  24,  1909,  1  p. 

Separation  of  slime  in  cyanide  treatment.  M.  &  S.  P.,  Apr.  25,  1908, 
4pp. 

Theory  of  settlement  of  slime.  M.  &  S.  P.,  July  11,  1908,  2  pp.;  June  12 
and  Aug.  21,  1909,  2  pp. 

Treatment  of  slime.     Min.  Mag.,  Nov.,  1909,  4  pp. 

PARKISH,  E.     Slime.     M.  &  S.  P.,  Oct.  9,  1909,  1  p. 

PRISTER,  A.  Coagulation  and  rapid  settlement  of  slime.  Proc.  Ch.  & 
Met.  Soc.,  S.  A.,  vol.  2,  1898,  4  pp. 

SALKINSON,  A.  Utilization  of  waste  heat  in  slime  settlement.  Jour.  Ch., 
Met.,  &  Min.  Soc.,  S.  A.,  June  to  Nov.,  1907,  12  pp.;  Mar.,  1909,  2  pp. 

SCOBY,  J.  C.  Economy  in  mill  water.  (Dewatering  tank  and  device.) 
Eng.  &  Min.  Jour.,  Dec.  10,  1903,  2  pp.  "Notes  on  Metallurgical  Mill  Con- 
struction. " 

SPERRY,  E.  A.  Handling  slime,  with  special  reference  to  sizing  and  classi- 
fication. West.  Ch.  &  Met.,  Mar.,  1908,  12  pp. 

STRICKLAND,  H.  Decantation  tank  for  utilizing  waste  water.  Min.  Sci., 
Oct.  7,  1909,  2  pp. 

SULMAN,  H.  L.  Slime  settlement.  Eng.  &  Min.  Jour.,  Oct.  31,  1908; 
abstract  from  Inst.  Min.  &  Met. 

TAYS,  E.  A.  H.  Experience  in  water  recovery..  (Slime  settling.)  M.  & 
S.  P.,  Aug.  19  and  Oct.  28,  1905,  1  p. 

WIARD,  E.  S.  Syphon  device  for  removing  floating  material.  M.  &  S.  P. 
Feb.  2,  1907,  1  p.  "Recent  Cyanide  Practice,"  p.  215. 

WILLIS,  H.  T.     Separation  and  settlement  of  slime.     M.  &  S.  P.,  July  25, 

1908,  1  p. 

Engineering  and  Mining  Journal.  Method  of  handling  slime  and  tailing. 
(Conveying  and  dewatering.)  Eng.  &  Min.  Jour.,  Apr.  9,  1910,  1  p. 

South  African  Mining  Journal.  Sand  classification  on  Rand.  (Diaphragm 
classifiers.)  July  1,1911. 

K.     Sand  Treatment  and  Percolation 

ALDERSON,  M.  W.  Cyaniding  slimy  ores  and  tailing.  M.  &  S.  P.,  June  3 
to  July  1,  1899,  5  pp. 

BOTSFORD,  R.  S.  Method  of  leaching  gold  ore  tailing.  Inst.  Min.  &  Met., 
vol.  16,  1907,  1  p. 

CALDECOTT,  W.  A.  Use  of  vacuum  pump  in  cyaniding  of  sand.  Jour. 
Ch.,  Met.,  &  Min.  Soc.,  S.  A.,  Jan.,  1909,  1  p.;  abstract  in  M.  &  S.  P.,  Feb.  27, 

1909,  1  p. 

CALDECOTT  (W.  A.)  and  JOHNSTON  (A.  M.).  Elimination  of  gold-bearing 
solution  from  sand.  Jour.  Ch.,  Met.,  &  Min.  Soc.,  S.  A.,  Nov.,  1907,  1  p. 

CROSSE,  A.  F.  Treatment  of  slimy  material  with  cyanide.  Min.  World, 
Feb.  12,  1910,  2  pp.;  abstract  from  Jour.  Ch.,  Met.,  &  Min.  Soc.,  S.  A. 

DENNY,  H.  S.  Cyanide  treatment  of  sand  on  the  Rand.  M.  &  S.  P., 
Sept.  19,  1903,  2  pp.;  abstract  from  Jour.  Ch.,  Met.,  &  Min.  Soc.,  S.  A. 


CLASSIFIED  BIBLIOGRAPHY  231 

DURANT,  H.  T.  Upward  leaching  of  sand.  Eng.  &  Min.  Jour.,  Feb.  25, 
1911,  1  p. 

FELL,  E.  N.  Treatment  of  tailing  by  the  cyanide  process  at  Athabasca 
mine,  Nelson,  B.  C.  T.  A.  I.  M.  E.,  vol.  31,  1900,  12  pp. 

IHLSENG,  A.  O.  Method  of  handling  slime  and  tailing.  Eng.  &  Min. 
Jour.,  Apr.  9,  1910,  1  p.  -. 

LINDEN,  H.  I.     Leaching  slimy  pulp.     Pac.  Miner,  Dec.,  1909,  1  p. 

MEGRAW,  H.  A.  Some  characteristics  of  sand  in  cyaniding.  Min.  World, 
May  7,  1910,  2  pp. 

OHLY,  J.     Modern  leaching  processes.     M.  &  S.  P.,  vol.  82,  p.  168,  1  p. 

PENGILLY,  F.  C.  On  successful  treatment  of  tailing  by  direct-filling  process 
on  the  Witwatersrand.  Inst.  Min.  &  Met.,  vol.  6,  1897,  7  pp.;  abstract  in 
M.  &  S.  P.,  June  4,  1898,  1  p. 

PRISTER,  A.  Some  suggestions  on  cyaniding  of  tailing.  Jour.  Ch.,  Met., 
&  Min.  Soc.,  S.  A.,  Oct.  and  Dec.,  1905. 

TAYS,  E.  A.  H.  Cyanide  notes.  (On  leaching  and  aeration.)  M.  &  S.  P., 
Sept.  1,  1906,  2  pp. 

TRUSCOTT  (S.  J.)  and  YATES  (A.).  Proposed  method  of  treating  sand 
residue  dumps.  Jour.  Ch.,  Met.,  &  Min.  Soc.,  S.  A.,  Jan.,  1906,  2  pp.  July, 

1906,  Mar.,  1907,  1  p. 

WHITE,  H.  A.     Last  drainings.     Jour.  Ch.,  Met.,  &  Min.  Soc.,  S.  A.,  Feb., 

1907,  5  pp.;  June,  1907,  4  pp.;  July,  1907,  1  p. 

Engineering  and  Mining  Journal.  Godbe  agitation  method  of  leaching. 
Vol.  73,  p.  321. 

Sand  treatment  chart  and  record.     May  16,  1908. 

Mining  and  Scientific  Press.  Godbe  method  of  leaching  by  agitation. 
M.  &S.  P.,  Jan.  25,  1902/ 

The  leaching  process.  Vol.  48,  pp.  254,  274,  and  290. 
Treatment  of  tailing  by  cyaniding.  Vol.  82,  p.  115. 
Treatment  of  tailing  in  South  Africa.  Mar.  2,  1901,  1  p. 

L.     Slime  Treatment,  Agitation,  and  Decantation 

AD  AIR,  A.  Adair-Usher  process.  Jour.  Ch.,  Met.,  &  Min.  Soc.,  S.  A., 
May,  1908,  9  pp.;  July,  1  p.;  Aug.,  2  pp.;  Sept.,  2  pp.;  Oct.,  1  p.;  Nov.,  1908, 
4pp. 

ADAMS,  H.  Air  agitation  of  slime  in  Pachuca  tanks.  Min.  World,  Apr.  1, 
1911;  abstract  in  Pac.  Miner,  Apr.,  1911. 

Continuous  cyaniding  in  Pachuca  tanks.  Min.  &  Eng.  World,  Sept.  2, 
1911,  2  pp.;  abstract  from  Trans.  A.I.M.E.,  Aug.,  1911. 

ADENDORF,  J.  E.  R.  Experiments  in  treatment  of  accumulated  ore  slime 
by  air-lift  agitation.  Jour.  Ch.,  Met.,  &  Min.  Soc.,  S.  A.,  July,  1911,  4  pp.; 
S.  A.  Min.  Jour.,  July  29,  1911,  2  pp. 

ALLEN,  R.  Air-lift  agitation  of  slime  pulp.  Jour.  Ch.,  Met.,  &  Min. 
Soc.,  S.  A.,  Mar.,  1911,  3  pp.;  April,  1911,  4  pp.;  June,  1911,  2  pp. 

APLIN,  D.  G.     Slime  treatment.     M.  &  S.  P.,  Jan.  23,  1904,  1  p. 

BETTEL,  W.  Slime  treatment  by  Adair-Usher  process.  S.  A.  Min.  Jour., 
Nov.  6,  1909,  1  p. 


232          TEXT  BOOK  OF  CYANIDE  PRACTICE 

BRODIE,  W.  Cyanide  lixiviation  by  agitation.  Eng.  &  Min.  Jour.,  Apr. 
3,  1909,  1  p. 

BROWN,  F.  C.  Agitation  by  compressed  air  with  Brown  tanks.  M.  &  S.  P., 
Sept.  26,  1908,  3  pp.  "More  Recent  Cyanide  Practice,"  p.  210. 

B.  and  M.  circulating  tank.     N.  Z.  Mines  Record,  Oct.  16,  1907,  5  pp. 

BUEL,  J.  F.  Modified  form  of  Pachuca  tank.  Min.  &  Eng.  World,  Nov. 
11,  1911. 

CALDECOTT,  W.  A.  Discrepancies  in  slime  treatment.  (Including  sub- 
ject of  specific  gravity  with  complete  specific  gravity  table  of  slime  pulp.) 
Proc.  Ch.  &  Met.  Soc.,  S.  A.,  vol.  2,  1898,  17  pp. 

Solution  of  gold  in  accumulated  and  other  slime.  Proc.  Ch.  &  Met.  Soc., 
S.  A.,  vol.  2,  1897,  6  pp. 

CARTER,  T.  L.     Slime  problem.     Eng.  &  Min.  Jour.,  Mar.  27,  1904,  3  pp. 

CLARK,  W.  C.     Saving  slime.     Mines  &  Mins.,  vol.  21,  p.  343,  1  p. 

CROSSE,  A.  F.  Treatment  of  ore  slime.  Jour.  Ch.,  Met.,  &  Min.  Soc., 
S.  A.,  Nov.,  1909,  2  pp.;  abstract  in  Eng.  &  Min.  Jour.,  Feb.  26,  1910. 

DE  KALB,  C.  Trapezoidal  slime  agitator.  Eng.  &  Min.  Jour.,  vol.  77, 
p.  241,  1  p. 

DENNY,  H.  S.  Slime  treatment  on  the  Rand.  Eng.  &  Min.  Jour.,  Oct.  24, 
1903,  3  pp. 

DORR,  J.  V.  N.  Continuous  cyanidation.  Met.  &  Chem.  Eng.,  Sept., 
1911,  1  p. 

EGGERS,  J.  H.  Continuous  agitation  and  decantation  in  Pachucas.  Pac. 
Miner,  Feb.,  1911,  1  p. 

EHRMANN,  L.  Sampling,  analyzing,  and  treating  slime.  Proc.  Ch.  &  Met1. 
Soc.,  S.  A.,  vol.  2,  1899,  8  pp. 

FLEMING,  J.  Extraction  of  gold  from  cyanide  house  slime  by  a  wet  method. 
Proc.  Ch.  &  Met.  Soc.,  S.  A.,  vol.  3,  1903,  12  pp.;  abstract  in  Eng.  &  Min. 
Jour.,  Sept.  5,  1903,  1  p. 

FRASER,  L.  New  cyanide  device  for  agitating.  M.  &  S.  P.,  Oct.  15,  1910, 
Ip. 

Notes  on  slime  treatment  process.     Min.  World,  July  17,  1909,  1  p. 

FULTON,  C.  H.  Treatment  of  slime  by  cyanidation  in  Black  Hills.  Eng. 
&  Min.  Jour.,  Nov.  3,  1904,  1  p. 

GLAZE,  H.  L.  Principles  of  air-lift  pumps  (and  agitators).  Min.  &  Eng. 
World,  Sept.  23,  1911. 

GROTHE,  A.  Notes  on  cyaniding  in  Pachuca  tanks  and  continuous  system. 
Mex.  Min.  Jour.,  Aug.,  1910,  3  pp. 

Principles  governing  agitation  in  Pachuca  tanks.  Min.  World,  May  27, 
1911,  1  p. 

Principles  of  agitation  in  Pachuca  tanks.  M.  &  S.  P.,  July  15,  1911;  Mex. 
Min.  Jour.,  July,  1911. 

HALEY,  C.  S.  Recent  progress  in  slime-filtration  development.  M.  & 
S.  P.,  July  1,  1911,  1  p. 

HURTER,  C.  L.  Agitation  process  for  cyaniding  slime.  Eng.  &  Min. 
Jour.,  Jan.  19,  1901,  1  p. 

IRWIN,  D.  F.     Continuous  decantation.     M.  &  S.  P.,  July  22,  1911. 

JAMES,  A.     Lixiviation  of  slime.     Eng.  &  Min.  Jour.,  vol.  67,  p.  378. 


CLASSIFIED  BIBLIOGRAPHY  233 

Notes  on  process  for  treating  slime  without  filtration  or  decantation.  Inst. 
Min.  &  Met.,  vol.  7,  1898,  11  pp.  " 

JAY,  C.  H.  Continuous  dewatering,  agitating,  and  filtering  cyanide  process. 
Min.  Sci.,  June  3,  1909,  2  pp. 

KLUG,  G.  C.  Slime  treatment  for  extraction  of  gold.  Jour.  W.  A.  Cham, 
of  Mines,  June  30,  1910,  4  pp. 

KNIFFEN,  L.  M.  Metnods  of  pulp  agitation.  M.  &  S.  P.,  June  4,  1910, 
1  p.  "More  Recent  Cyanide  Practice, "  p.  401. 

KURYLA,  M.  H.  Continuous  Pachuca  tank  agitation  at  Esperanza  mill. 
Trans.  Mex.  Inst.,  Apr.,  1910,  7  pp.;  abstract  in  Eng.  &  Min.  Jour.,  July  30, 

1910,  1  p.;  abstract  in  Min.  World,  July  9,  1910,  1  p. 

Continuous  agitation  process  with  bottom  drive  storage  tank  at  Esperanza 
mill.  Mex.  Min.  Jour.,  Aug.,  1910,  2  pp. 

LAMB,  M.  R.  Charge  and  series  systems  of  cyaniding  slime.  Min.  World, 
Feb.  19,  1910,  2  pp.;  abstract  from  T.  A.  I.  M.  E. 

Cyaniding  slime.     T.  A.  I.  M.  E.,  vol.  40,  1909,  5  pp.;  vol.  41,  1910,  6  pp. 

New  cyanide  plant.     M.  &  S.  P.,  Dec.  29,  1906,  2  pp. 

Notes  on  air  agitation.  (Pachuca  tank.)  Eng.  &  Min.  Jour.,  Nov.  7, 
1908,  1  p. 

Present  tendencies  in  cyanide  practice.  Eng.  &  Min.  Jour.,  Oct.  29,  1910, 
4  pp. 

Progress  and  developments  in  cyanide  practice.  Eng.  &  Min.  Jour.,  Jan. 
15,  1910,  2  pp. 

Rapid  estimation  of  slime  pulp  in  cyanide  tanks.  (With  specific  gravity 
table.)  Eng.  &  Min.  Jour.,  Jan.  15,  1910,  1  p. 

Sliming  ore  for  cyanidation.  M.  &  S.  P.,  Nov.  23,  1908,  1  p.  "More 
Recent  Cyanide  Practice,"  p.  37. 

LASCHINGER,  E.  J.  Decantation  process  of  slime  treatment.  Jour.  Ch., 
Met.,  &  Min.  Soc.,  S.  A.,  Apr.,  1904,  16  pp.;  May,  1904,  1  p.;  abstract  in  Eng. 
&  Min.  Jour.,  Sept.  29,  1904,  2  pp. 

LASCHINGER,  E.  J.     Air-lift  agitation  of  slime  pulp.     Mines  &  Mins.,  Nov., 

1911,  3  pp. 

LEAVER,  E.  S.  Milling  practice  at  Nevada-Gold  field  Reduction  Works. 
M.  &  S.  P.,  Aug.  22,  1908,  1  p.  "More  Recent  Cyanide  Practice,"  p.  198. 

LOEVY  (J.)  and  WILLIAMS  (J.  R.).  Composition  of  slime  from  ore.  Proc. 
Ch.  &  Met.  Soc.,  S.  A.,  vol.  2,  1898,  2  pp. 

LYLE,  G.  G.  Solis  compressed-air  slime  agitator.  West.  Ch.  &  Met.,  Dec., 
1907,  4  pp. 

McCANN,  F.  Proposed  new  system  for  cyanide  treatment  of  slime.  Can. 
Min.  Jour.,  Sept.  15,  1909,  3  pp.;  Min.  World,  Nov.  6,  1909,  2  pp.;  abstract 
from  Trans.  Mex.  Inst. 

MACDONALD,  B.  Improvements  in  cyanide  process.  (Agitation  tank.) 
M.  &  S.  P.,  May  28,  1910,  2  pp.  "  More  Recent  Cyanide  Practice, "  p.  396. 

MACDOXALD,  B.  Parral  tank  system  of  slime  agitation.  Min.  &  Eng. 
World,  Oct.  28,  1911,  3  pp.;  abstract  from  Trans.  A.I.M.E. 

MclxTYRE,  A.  C.     A.  Z.  agitator.     Pac.  Miner,  Jan.,  1910,  2  pp. 

MEGRAW,  H.  A.  All-slime  treatment  of  ore  in  cyanide  plant.  Eng.  & 
Min.  Jour.,  Feb.  5,  1910,  2  pp. 


234          TEXT  BOOK  OF  CYANIDE  PRACTICE 

Discussion  of  some  continuous  processes  for  cyanide  treatment  of  silver- 
gold  ores.  Mex.  Min.  Jour.,  Aug.,  1910,  4  pp. 

What  is  a  slime?     Eng.  &  Min.  Jour.,  Nov.  3,  1904. 

MENNELL,  J.  L.  Continuous  cyanide  treatment.  Mex.  Min.  Jour.,  Feb., 
1909,  3  pp. 

NAHL,  A.  C.  Nahl  intermittent  slime  decanter.  Eng.  &  Min.  Jour.,  Feb. 
11,  1911,  1  p. 

NARVAEZ,  F.  Cyanidation  with  Brown  vat.  M.  &  S.  P.,  Nov.  30,  1907, 
1  p.  "More  Recent  Cyanide  Practice,"  p.  60. 

O'HARA,  J.  D.  Treatment  of  accumulated  slime.  Mex.  Min.  Jour., 
Sept.,  1910,  2  pp. 

PEAD,  C.  H.  Notes  on  improvements  in  cyanide  treatment  of  sands  and 
slimes.  Jour.  Ch.,  Met.,  &  Min.  Soc.,  S.  A.,  Sept.,  1905,  2  pp.;  Dec.,  1905, 
1  p.;  Jan.,  1906,  2  pp.;  Feb.,  1906,  2  pp. 

PEARCE,  S.  H.  Assay  of  slime  residue.  (Discrepancies.)  Jour.  Ch.,  Met., 
&  Min.  Soc.,  S.  A.,  May,  1909,  1  p. 

Cyaniding  low  grade  slime.  M.  &  S.  P.,  Nov.  28,  1903,  1  p.;  abstract 
from  Jour.  Ch.,  Met.,  &  Min.  Soc.,  S.  A. 

RAND,  E.  T.  Continuous  process  of  slime  treatment.  Proc.  Ch.  &  Met. 
Soc.,  S.  A.,  vol.  2,  1899,  9  pp. 

ROTHWELL,  J.  E.  Continuous  cyanide  treatment.  Met.  &  Chem.  Eng., 
July,  1911,  1  p. 

Counter-current  of  continuous  agitation,  decantation,  and  dilution  applied 
to  cyanide  process.  Met.  &  Chem.  Eng.,  Sept.,  1911,  2  pp. 

SHARWOOD,  W.  J.  What  constitutes  a  slime.  Eng.  &  Min.  Jour.,  Oct.  10 
and  31,  1903,  1  p. 

SPILSBURY,  E.  G.  Improvement  in  cyanide  practice.  (Just  silica  brick 
agitation  process.)  T.  A.  I.  M.  E.,  vol.  41,  1910,  14  pp.;  abstracts  in  Eng.  & 
Min.  Jour.,  Mar.  26,  1910,  1  p.;  in  Min.  Sci.,  June  9,  1910,  5  pp.;  in  Min. 
World,  June  4,  1910. 

STACKPOLE,  M.  D.  New  treatment  of  slime  problem  in  cyaniding  talcose 
ores.  Eng.  &  Min.  Jour.,  July  12,  1902,  1  p. 

STARBIRD,  H.  B.  New  system  for  cyanide  treatment  of  slime.  Mex.  Min. 
Jour.,  Dec.,  1909. 

SWAREN,  J.  W.  Historical  notes  on  air-lift  agitators.  M.  &  S.  P.,  Sept.  30, 
1911. 

SYMONDS,  L.  Notes  on  treatment  of  gold  slime  in  Venezuela.  Inst.  Min. 
&  Met.,  vol.  12,  1903,  7  pp. 

TAYS  (E.  A.  H.)  and  SCHIERTZ  (F.  A.).  Treatment  of  clay  slime  by  cyanide 
process  and  agitation.  T.  A.  I.  M.  E.,  vol.  32,  1901,  36  pp.;  abstract  in  M.  & 
S.  P.,  Feb.  15  to  Mar.  15,  1902,  6  pp. 

TORRENTE,  M.  Improvements  in  slime  treatment.  Jour.  Ch.,  Met.,  & 
Min.  Soc.,  S.  A.,  vol.  5,  p.  46,  1904,  6  pp. 

VON  BERNEWITZ,  M.  W.  Slime  agitation  at  Kalgoorlie.  M.  &  S.  P.,  June 
3,  1911,  2  pp. 

WARWICK,  A.  W.  Mechanical  air  agitation  for  slime  treatment.  Min. 
World,  Jan.  28,  1911,  2  pp.;  Apr.  22,  1911,  1  p. 

WILLIAMS,  J.  R.  Indirect  advantages  of  a  slime  plant.  Proc.  Ch.  &  Met. 
Soc.,  S.  A.,  vol.  2,  1899,  16  pp. 


CLASSIFIED  BIBLIOGRAPHY  235 

Treatment  of  battery  slime.     Proc.  Ch.  &  Met.  Soc.,  S.  A.,  vol.  2, 1897,  6  pp. 

WILSON,  E.  B.  Cyaniding  slime.  Mines  &  Mins.,  Sept.,  1908,  3  pp.; 
Oct.,  1908,  5  pp.;  Nov.,  1908;  Dec.,  1908. 

YAGER,  A.  J.  Modification  of  Pachuca-tank  practice.  (Also  concerning 
zinc-dust  precipitation.)  M.  &  S.  P.,  Oct.  22  and  Dec.  24,  1910;  abstract  in 
Pac.  Miner,  Nov.,  1910>  1  p. 

Australian  Mining  Standard.  Gold  saving  appliances.  (Agitator  and 
aerator.)  Oct.  20,  1909,  1  p. 

Usher  sand  process  for  extraction  of  gold.     Aug.  4,  1909,  2  pp. 

Engineering  and  Mining  Journal.     Cyanide  tank  record.     Jan.  29,  1910. 
Treatment  of  slime  in  tanks  with  conical  bottoms.     Mar.  28,  1903. 

Mexican  Mining  Journal.  Clear-solution  hydraulic  agitator.  Oct.,  1911, 
Ip. 

Mining  and  Engineering  World.  New  Patterson  agitator.  Oct.  21,  1911. 
Abstract  from  S.  A.  Min.  Jour. 

Mining  and  Scientific  Press.     Air-lift  agitation  of  slime  pulp.     May  6,  1911. 
Hydraulic  cyanide  tank.     Jan.  16,  1904. 
Modern  slime  plant.     Apr.  4,  1903,  1  p. 

Pacific  Miner.     Dilution  system  of  slime  treatment.     Dec.,  1909,  1  p. 

South  African  Mines.     Adair-Usher  process.     Apr.  20,  1907,  2  pp. 

M.  Filtration 

ALLEN,  A.  W.  Improvement  in  treatment  of  slime  by  vacuum  filter  proc- 
ess. Eng.  &  Min.  Jour.,  May  15,  1909,  1  p. 

BENNETT,  S.  E.  Treatment  of  slime  in  the  Black  Hills.  (Merrill  process.) 
Min.  World,  Feb.  22,  1908,  1  p.;  Min.  Sci.,  Feb.  27,  1908,  1  p. 

BOERICKE,  W.  F.     Sand  filters.     Eng.  &  Min.  Jour.,  Oct.  9,  1909. 

BOSQUI,  F.  L.     Moore  and  Butters  filters.     M.  &  S.  P.,  Feb.  2^1907,  1  p. 

Proposed  filter  press  slime  plant.  T.  A.  I.  M.  E.,  vol.  34,  1903,  13  pp.; 
abstract  in  M.  &  S.  P.,  Mar.  26  and  Apr.  2,  1904,  2  pp. 

Recent  improvements  in  cyanide  process.  M.  &  S.  P.,  Dec.  15,  1906,  2  pp.; 
Mines  &  Mins.,  vol.  27,  p.  298,  2  pp. 

BROWN,  R.  G.  Cyanide  practice  with  Moore  filter.  M.  &  S.  P.,  Sept.  1 
and  8,  1906,  6  pp.  "Recent  Cyanide  Practice, "  p.  92. , 

BURT,  E.  Burt  rapid  cyanide  filter.  M.  &  S.  P.,  Dec.  7,  1907,  2  pp. 
"More  Recent  Cyanide  Practice,"  p.  76. 

New  slime  filter  at  El  Oro,  Mexico.  Eng.  &  Min.  Jour.,  Jan.  21,  1911, 
2pp. 

CLEVENGER,  G.  H.  Butters  vacuum  filter.  Mines  &  Mins.,  July,  1908, 
3pp. 

DIXON,  C.  Notes  on  treatment  of  slime  by  filter  presses.  Proc.  Ch.  & 
Met.  Soc.,  S.  A.,  vol.  3,  1902,  33  pp. 

DOWLING,  W.  R.  Use  of  filter  presses  for  clarifying  decanted  slime  solu- 
tion. Jour.  Ch.,  Met.,  &  Min.  Soc.,  S.  A.,  June,  1908,  1  p. 

EDMANDS,  H.  R.  Filter-pressing  of  slime.  Eng.  &  Min.  Jour.,  May  25, 
1905,  1  p.;  abstract  from  Aust.  Inst.  Min.  Eng. 

EHLE,  M,     Homestake  slime  plant.     Mines  &  Mins.,  Mar.,  1907,  6  pp. 


236          TEXT  BOOK  OF  CYANIDE  PRACTICE 

FOOTE,  A.  D.  Tube-mill  lining,  slime  filters,  and  patents.  M.  &  S.  P., 
Feb.  1,  1908,  1  p.  "More  Recent  Cyanide  Practice,"  p.  111. 

FORBES,  D.  L.  H.  Filtration  of  slime  at  El  Oro.  Eng.  &  Min.  Jour., 
Sept.  5,  1908,  2  pp. 

FRIER,  J.  Butters  filter.  (Tonnage  and  costs  at  Copala,  Mex.)  M.  & 
S.  P.,  Apr.  6,  1907. 

HAMILTON,  E.  M.  Filtration  of  slime  by  Butters  method.  M.  &  S.  P., 
June  22  to  29,  1907,  10  pp.  "Recent  Cyanide  Practice,"  p.  269. 

HUNT,   B.     Continuous  vacuum-filter  machine.     M.  &  S.  P.,   Sept.  26, 

1908,  2  pp.     "More  Recent  Cyanide  Practice, "  p.  216. 

IRVIN,  D.  F.     Silver  on  filter  leaves.     M.  &  S.  P.,  Apr.  2,  1910. 

JAMES,  A.  Annual  cyanide  letter.  M.  &  S.  P.,  Jan.  1,  1910,  4  pp.;  dis- 
cussion by  E.  M.  Hamilton  and  J.  M.  Nicol,  Feb.  26,  1910;  by  R.  Nichols, 
Apr.  2,  1910;  by  M.  W.  von  Bernewitz,  May  28,  1910.  All  in  "More  Recent 
Cyanide  Practice, "  p.  362. 

JAY,  C.  H.  Continuous  dewatering,  agitating,  and  filtering  cyanide  proc- 
ess. West.  Chem.  &  Met.,  May,  1909,  5  pp. 

JENSEN,  E.  Simple  and  effective  contrivance  for  filtering  gold  slime. 
Jour.  W.  A.  Cham,  of  Mines,  Nov.  30,  1908,  2  pp.;  abstract  in  Eng.  &  Min. 
Jour.,  May  1,  1909,  1  p. 

KELLY,  D.  J.  Recent  improvements  in  art  of  slime  treatment.  West. 
Ch.  &  Met.,  Sept.,  1907,  10  pp.;  Mines  &  Mins.,  vol.  28,  p.  102,  3  pp. 

KIRBY,  A.  G.  Vacuum  slime  filters.  M.  &  S.  P.,  July  13,  1907,  3  pp. 
"Recent  Cyanide  Practice,"  p.  312. 

LAMB,  M.  R.  Butters  filter.  M.  &  S.  P.,  Jan.  12,  Feb.  2,  Mar.  23  and  30, 
1907.  "Recent  Cyanide  Practice, "  pp.  213  and  218. 

Butters  slime  filter  at  cyanide  plant  of  Combination  Mines  Co.,  Goldfield, 
Nev.  T.  A.  I.  M.  E.,  vol.  38,  1907,  10  pp. 

Ridgeway  filter.  M.  &  S.  P.,  June  6,  1908.  "More  Recent  Cyanide 
Practice,"  p.  145. 

McNEiL,  W.  Filter-press  treatment  of  gold  ore  slime.  (Hannan's,  West 
Australia.)  Inst.  Min.  &  Met.,  vol.  6,  1898,  22  pp.;  abstract  in  Eng.  &  Min. 
Jour.,  Dec.  31,  1898,  2  pp.;  abstract  in  M.  &  S.  P.,  June  17,  1899,  1  p. 

MARTIN,  A.  H.  Oliver  continuous  filter.  (At  Grass  Valley.)  M.  &  S.  P., 
Nov.  27,  1909,  1  p.  (At  Minas  del  Tajo,  Sinaloa,  Mex.)  M.  &  S.  P.,  July  24, 

1909.  Both  in  "More  Recent  Cyanide  Practice,"  p.  335. 

MERRILL,  C.  W.  Homestake  slime  plant  costs.  Eng.  &  Min.  Jour.,  Aug. 
22,  1908;  M.  &  S.  P.,  Sept.  12,  1908.  "More  Recent  Cyanide  Practice," 
p.  209. 

MOORE,  B.  H.  Review  of  various  slime  filter  types.  Min.  &  Eng.  World, 
Oct.  7,  1911,  2  pp. 

MOORE,  G.  Moore  process  at  Con.  Mercur  gold  mine.  Eng.  &  Min. 
Jour.,  Dec.  5,  1903,  1  p.;  M.  &  S.  P.,  Nov.  21,  1903,  1  p. 

NICHOLS,  A.     Vacuum  nitration.     M.  &  S.  P.,  Mar.  12,  1910,  1  p. 

NUTTER,  E.  H.  Cyanide  practice  with  Moore  filter  at  Liberty  Bell  mine. 
M.  &  S.  P.,  Dec.  15,  1906,  and  Feb.  16,  1907,  4  pp.  "Recent  Cyanide  Prac- 
tice, "  pp.  174  and  225. 

OATES,  J.  H.     Improvements  to  filter  plants.     Mex.  Min.  Jour.,  Sept.,  1911. 


CLASSIFIED   BIBLIOGRAPHY  237 

O'HARA,  J.  D.  Treatment  of  accumulated  slime  and  use  of  filter  presses 
for  clarifying  slime  solution  and  by-products.  Jour.  Ch.,  Met.,  &  Min.  Soc., 
S.  A.,  Apr.,  1910,  3  pp.;  May,  1910,  2  pp. 

PARRISH,  E.     Filtration  of  slime.     Pac.  Miner,  Oct.,  1909,  4  pp. 

Parrish  continuous  filter.     Eng.  &  Min.  Jour.,  June  2,  1906,  1  p. 

Treatment  of  slime.     (Leaf  filtration.)     M.  &  S.  P.,  Feb.  9,  1907,  1  p. 

PORTER  (J.  E.)  and  CLARK  (A.  L.).  Apparatus  for  extracting  and  filtering 
ore.  Min.  World,  Sept.  12,  1908,  2  pp. 

PRICHARD,  W.  A.  Filter-pressing  in  Western  Australia.  Eng.  &  Min. 
Jour.,  Apr.  14,  1904,  2  pp. 

PUTMAN,  D.  G.  Data  on  low  mechanical  loss  of  cyanide  with  Kelly  filter. 
M.  &  S.  P.,  Jan.  16,  1909.  "More  Recent  Cyanide  Practice,"  p.  247. 

SCHORR,  R.  Continuous  slime  filter.  M.  &  S.  P.,  Aug.  8,  1908,  2  pp. 
"  More  Recent  Cyanide  Practice, "  p.  194. 

SMITH,  A.  M.  Vacuum  slime-filters  at  Nevada-Goldfield  Reduction  Works. 
M.  &  S.  P.,  July  10,  1909,  1  p.  "More  Recent  Cyanide  Practice," 
p.  279. 

STEVENS,  T.  B.  Estimation  of  capacity  of  vacuum  filter  plants.  Jour. 
W.  A.  Cham,  of  Mines,  Nov.  30,  1909,  3  pp. 

STEVENS  (T.  B.)  and  DEGENHARAT  (W.  R.).  Retreatment  of  tailing  at 
Oroya-Brownhill  and  vacuum  filter  practice.  Jour.  W.  A.  Cham.  Mines, 
Mar.,  1911.  Abstract  in  Met.  &  Chem.  Eng.,  July,  1911;  in  Min.  Mag., 
June,  1911;  in  Eng.  &  Min.  Jour.,  Sept.  2,  1911. 

SWEETLAND,  W.  J.  Pressure  filtration.  M.  &  S.  P.,  Dec.  25,  1909,  2  pp. 
"More  Recent  Cyanide  Practice,"  p.  356. 

Sweetland  filter  press.  Eng.  &  Min.  Jour.,  Feb.  15,  1908,  1  p.;  M.  &  S.  P., 
Nov.  7,  1908,  1  p.;  Min.  World,  Oct.  10,  1908,  1  p.;  Pac.  Miner,  Mar.,  1910, 
3pp. 

TRUSCOTT  (S.  J.)  and  YATES  (A.).  Notes  on  use  of  filter  press  for  clarifying 
solutions.  Jour.  Ch.,  Met.,  &  Min.  Soc.,  S.  A.,  July,  Aug.,  Sept.,  1906;  Feb., 
Apr.,  1907,  5  pp. 

TWEEDY  (G.  A.)  and  BEALS  (R.  L.).  Oliver  continuous  filter  at  Minas  del 
Tajo.  Eng.  &  Min.  Jour.,  Mar.  5,  1910,  2  pp.;  abstract  from  T.  A.  I.  M.  E., 
vol.  41,  1910. 

VON  BERNEWITZ,  M.  W.  Filter-pressing  slime.  Pac.  Miner,  Nov.,  1910, 
1  p.;  abstract  from  Proc.  Aust.  Inst.  Min.  Engrs. 

Slime  treatment  at  Kalgoorlie.  M.  &  S.  P.,  Dec.  14,  1907,  1  p.  "More 
Recent  Cyanide  Practice, "  p.  82. 

Eclipse  slime  filter.  Min.  &  Eng.  Rev.,  Aug.  5,  1911;  abstract  in  Min.  & 
Eng.  World. 

WADE,  E.  M.    Wade  vacuum  filter.     West.  Ch.  &  Met.,  Sept.,  1907,  4  pp. 

WALKER,  E.  N.  Continuous  slime  filter.  (Describes  solution  sand  filter 
only.)  M.  &  S.  P.,  Oct.  17,  1908,  1  p.  "More  Recent  Cyanide  Practice," 
p.  198. 

WALLACE,  A.  B.  Filter-press  practice  in  Western  Australia.  M.  &  S.  P., 
Feb.  3,  1906,  1  p.  "Recent  Cyanide  Practice,"  p.  18. 

WALSH,  G.  E.  Application  of  eyaniding  and  filter-pressing.  Eng.  &  Min. 
Jour.,  vol.  81,  p.  488,  1  p, 


238          TEXT  BOOK  OF  CYANIDE  PRACTICE 

WOOD,  G.  W.  Boston-Sunshine  mill.  (Moore  process.)  M.  &  S.  P., 
Aug.  28,  1909,  1  p.  ''More  Recent  Cyanide  Practice,"  p.  303. 

YOUNG,  G.  J.  Slime  filtration.  Trans.  A.I.M.E.,  Oct.,  1911.  Abstract  in 
Eng.  &  Min.  Jour.,  Nov.  4,  1911,  4  pp.;  in  M.  &  S.  P.,  Oct.  28,  1911. 

Engineering  and  Mining  Journal.  Continuous  filter  press.  Oct.  17,  1903, 
lp. 

Grothe-Carter  vacuum  filter.     Sept.  3,  1910,  1  p. 
Improvements  in  treatment  of  slime  by  vacuum  filter  press  process. 
(Type  of  leaf  filter.)     May  15,  1909,  1  p. 

Ogle  continuous  filter.     Feb.  23,  1905,  1  p. 

Mexican  Mining  Journal.  Hunt  continuous  slime  filter.  Sept.,  1909, 
2pp. 

Mines  and  Minerals.     Burt  revolving  filter.     Nov.,  1911,  2  pp. 
Mining  and  Scientific  Press.     Filter  press  treatment  of  gold  ore  and  slime 
by  cyanide.     July  4  and  11,  1903,  3  pp. 

New    continuous    filtering    and    straining    machine.     (Trent    filter.) 
Feb.  22,  1908,  1  p. 

Ridgeway  filter     Feb.  9,  1907,  2  pp.     "Recent  Cyanide  Practice," 
p.  221;  abstract  from  Jour.  W.  A.  Cham,  of  Mines. 
Mining  World.     Portland  continuous  slime  filter.     Dec.  17,  1910,  1  p. 

Treatment  of  slime  in  Black  Hills.     (Merrill  process.)     Feb.  22,  1908, 
lp. 

South  African  Mining  Journal.  Butters  filter  at  Crown  mines.  Aug.  27, 
1910,  1  p. 

N.    Precipitation 

ALDERSON,  M.  W.  Successful  precipitation  from  solutions  weak  in  cyanide. 
M.  &  S.  P.,  Mar.  24,  1900,  1  p. 

BALDWIN,  A.  G.     Zinc  shavings.     Mex.  Min.  Jour.,  Oct.,  1908,  1  p. 

BEADLE,  A.  A.  Electric  reduction  of  gold  from  cyanide  solutions.  M.  & 
S.  P.,  Jan.  30,  1904,  1  p. 

BOSQUI,  F.  L.  Absorption  of  gold  by  wooden  leaching  tanks.  Eng.  & 
Min.  Jour.,  vol.  65,  p.  248,  1  p. 

Cause  of  short  zinc.  M.  &  S.  P.,  Apr.  3,  1909.  "More  Recent  Cyanide 
Practice,"  p.  273. 

BRAZIER,  H.  A.  Grinding  machine  for  zinc-cutting  tools.  Jour.  Ch., 
Met.,  &  Min.  Soc.,  S.  A.,  Jan.,  1911,  1  p. 

BROWNE,  R.  S.  Cause  of  short  zinc.  M.  &  S.  P.,  May  22,  1909,  1  p. 
"More  Recent  Cyanide  Practice,"  p.  275. 

BUSEY,  A.  P.  Methods  of  precipitation  in  cyanide  process.  Colo.  Sch.  of 
Mines  Bull.,  Jan.,  1907,  21  pp. 

CARTER,  T.  L.  Zinc  process  for  precipitating  gold  from  weak  solutions. 
Proc.  Ch.  &  Met.  Soc.,  S.  A.,  vol.  2,  1898,  72  pp. 

CALDECOTT,  W.  A.  Precipitation  of  gold  by  carbonaceous  matter.  M.  & 
S.  P.,  June  12,  1909,  2  pp.;  Min.  World,  Oct.  9,  1909;  abstract  from  Jour.  Ch., 
Met.,  &  Min.  Soc.,  S.  A. 

Use  of  vats  in  place  of  zinc  boxes.  Proc.  Ch.  &  Met.  Soc.,  S.  A.,  vol.  2, 
1899,  3  pp.;  abstract  in  Eng.  &  Min.  Jour.,  Nov.  18,  1899,  1  p. 


CLASSIFIED  BIBLIOGRAPHY  239 

CALDECOTT  (W.  A.)  and  JOHNSON  (E.  H.).  Precipitation  of  gold  from 
cyanide  solutions.  Jour.  Ch.,  Met.,  &  Min.  Soc.,  S.  A.,  July,  1903,  5  pp.; 
Dec.,  1903,  3  pp.;  Feb.,  1904,  1  p.;  abstract  in  Eng.  &  Min.  Jour.,  Nov.  21, 

1903,  2  pp. 

CHRISTY,  S.  B.  Solution  and  precipitation  of  cyanide  of  gold.  T.  A.  I. 
M.  E.,  vol.  26,  1896,  37  pp.;  vol.  28,  1898,  25  pp.;  discussion  in  Proc.  Ch.  & 
Met.  Soc.,  S.  A.,  vol.  2,  1897. 

CLARK,  A.  J.  Precipitation  from  cyanide  solutions  by  zinc  shavings  and 
dust.  A  comparison  of  results  and  costs.  Jour.  Ch.,  Met.,  &  Min.  Soc., 
S.  A.,  Jan.,  1909,  2  pp.;  abstract  in  Min.  World,  Apr.  3,  1909,  1  p. 

Zinc-dust  precipitation.     Min.  Mag,  Apr.,  1911,  1  p. 

CLARK  (A.  J.)  and  SHARWOOD  (W.  J.).  Notes  on  precipitating  effects  of 
substances  containing  various  forms  of  carbon  and  cellulose,  on  cyanide 
solutions  containing  gold  and  silver.  Jour.  Ch.,  Met.,  &  Min.  Soc.,  S.  A., 
Jan.,  1904,  4  pp.;  abstract  in  M.  &  S.  P.,  Apr.  16,  1910,  3  pp. 

CLARK,  J.  E.     Soluble  gold  slime.     M.  &  S.  P.,  Sept.  24,  1910. 

COLBATH,  J.  S.  Automatic  zinc  dust  feeder.  Eng.  &  Min.  Jour.,  Feb.  26, 
1910,  1  p. 

Iron  screens  in  zinc  boxes.     (Inadvisable.)     M.  &  S.  P.,  Jan.  25,  1908. 

COOLIDGE,  R.  F.  Investigation  of  zinc-box  white  precipitate.  West.  Ch. 
&  Met.,  Aug.,  1909,  9  pp. 

Precipitation  and  clean-up  at  Kendall  mill,  Kendall,  Montana.  West. 
Ch.  &  Met.,  Aug.,  1908,  3  pp. 

WTiite  precipitate  found  in  zinc  boxes.     Min.  Sci.,  July  29,  1909,  2  pp. 

Zinc-box  white  precipitate.     M.  &  S.  P.,  Sept.  18,  1909,  2  pp. 

CowpER-CoLES,  S.  Some  notes  on  recovery  of  gold  from  cyanide  solutions. 
Inst.  Min.  &  Met.,  vol.  6,  1898,  10  pp. ;  abstract  in  Eng.  &  Min.  Jour.,  Aug.  6, 
1898,  1  p.;  abstract  in  M.  &  S.  P.,  Nov.  26,  1898,  1  p. 

CRANE,  W.  R.  Bibliography  of  electro-metallurgy.  In  'Index  of  Mining 
Engineering  Literature, "  1909,  4  pp. 

CROGHAN,  E.  H.  Experiments  on  precipitation  of  gold  from  cyanide 
solution  by  carbon  in  lime.  Jour.  Ch.,  Met.,  &  Min.  Soc.,  S.  A.,  May,  1910, 
3  pp.;  July,  1910,  2  pp.;  Oct.,  1910,  2  pp. 

EHRMANN,  L.  Precipitation  of  gold  from  cyanide  solutions.  Proc.  Ch.  & 
Met.  Soc./S.  A.,  vol.  2,  1897,  8  pp. 

EKELEY  (J.  B.)  and  TATUM  (A.  L.).  Electrochemistry  of  gold  cyanide 
solutions.  Min.  World,  Feb.  20,  1909,  1  p. 

FASSETT,  C.  M.     Hendryx  cyanide  process.     Eng.  &  Min.  Jour.,  May  5, 

1904,  1  p.;  M.  &  S.  P.,  Feb.  27,  1904,  1  p. 

HAMILTON,  E.  M.  Development  in  electrolytical  precipitation  of  gold  and 
silver  from  cyanide  solutions.  Jour.  Ch.,  Met.,  &  Min.  Soc.,  S.  A.,  Nov., 
1903,  8  pp. 

HARTLEY,  A.  H.  Precipitation  of  gold  from  cyanide  solutions.  Proc. 
Ch.  &  Met.  Soc.,  S.  A.,  vol.  2,  1899,  4  pp. 

HERRICK,  R.  L.  Precipitation  by  zinc  dust  at  Homestake  mill.  Mines  & 
Mins.,  Apr.,  1908,  1  p. 

HULT,  S.  B.  Slight  improvement  in  extractor  box.  Proc.  Ch.  &  Met. 
Soc.,  S.  A.,  vol.  3,  1902,  1  p. 


240          TEXT  BOOK  OF  CYANIDE  PRACTICE 

HUNT,  B.  Cause  of  short  zinc.  M.  &  S.  P.,  May  22,  1909.  "More 
Recent  Cyanide  Practice,  "  p.  274. 

JAMES,  A.  Notes  on  sump  solutions,  extractor-box  work,  and  cleaning- 
up  in  cyanide  process.  Inst.  Min.  &  Met.,  vol.  6,  1897,  12  pp.;  abstract  in 
Eng.  &  Min.  Jour.,  Sept.  11,  1897,  1  p.;  abstract  in  M.  &  S.  P.,  Nov.  8,  1902, 
lp. 

Precipitation  of  gold  by  zinc  thread  from  dilute  and  foul  cyanide  solutions. 
T.  A.  I.  M.  E.,  vol.  27,  1897,  5  pp. 

See  "Cyanide  Practice"  by  James  for  substance  of  above. 

JORY,  J.  H.  Electrolytic  precipitation  from  cyanide  solutions.  M.  &  S.  P., 
June  22,  1901,  1  p. 

KAEDING,  H.  B.     Short  zinc.     Mex.  Min.  Jour.,  Mar.,  1911,  1  p. 

LAMB,  M.  R.  Electrolytic  precipitation  at  Minas  Prietas.  Eng.  &  Min. 
Jour.,  Apr.  3,  1909,  1  p. 

Zinc  consumption  and  preparation.     Mex.  Min.  Jour.,  Sept.,  1908,  1  p. 

Zinc  dust  precipitation.  (Method  at  small  mill.)  M.  &  S.  P.,  Oct.  6, 
1906,  1  p.  "Recent  Cyanide  Practice,"  p.  134. 

LAMB,  R.  B.  Practical  hints  in  precipitation  of  silver  from  cyanide  solu- 
tions. Can.  Min.  Jour.,  Dec.  15,  1909,  2  pp.;  Min.  Sci.,  Dec.  23,  1909,  2  pp. 

LAY,  D.  Electrolysis  of  gold  from  cyanide  solution.  Eng.  &  Min.  Jour., 
Apr.  27,  1907,  3  pp. 

Electro-cyanide  processes.     Eng.  &  Min.  Jour.,  Apr.  11,  1908,  2  pp. 

LEINER,  T.  E.     Arsenic  in  zinc  boxes.     Pac.  Miner,  July,  1910. 

LINTON,  R.  Zinc  dust  precipitation  at  Cerro  Prieto.  Jour.  Ch.,  Met.,  & 
Min.  Soc.,  S.  A.,  Sept.,  1908,  to  Jan.,  1909,  6  pp. 

Zinc  dust  precipitation  at  Homestake  mine.  Jour.  Ch.,  Met.,  &  Min.  Soc., 
S.  A.,  July,  1909,  1  p. 

LLOYD  (W.  D.)  and  RAND  (E.  T.).  Rotary  extractor  for  precious  metals 
from  solutions.  Jour.  Ch.,  Met.,  &  Min.  Soc.,  S.  A.,  Dec.,  1909,  3  pp. 

LOWLES,  J.  I.  On  charcoal  precipitation  from  auro-cyanide  solutions. 
Inst.  Min.  &  Met.,  vol.  7,  1899,  8  pp.;  abstract  in  M.  &  S.  P.,  July  29,  1899. 

MACDONALD,  J.  J.  Some  laboratory  work  in  cyaniding.  (Regarding  pre- 
cipitation.) M.  &  S.  P.,  Mar.  12  and  19,  1904. 

MACKAY,  A.  N.  Precipitation  of  gold  from  cyanide  solutions  and  absorp- 
tion of  gold  by  wooden  vat.  Eng.  &  Min.  Jour.,  July  15,  1905;  M.  &  S.  P., 
June  17,  1905,  1  p. 

MEGRAW,  H.  A.  Precipitation  from  cyanide  solution.  (New  arrangement 
of  zinc  box.)  Eng.  &  Min.  Jour.,  Dec.  5,  1903,  1  p. 

Precipitation  of  gold  and  silver  in  cyaniding.  Eng.  &  Min.  Jour.,  Oct.  7, 
1911,  3  pp. 

MERRILL,  C.  W.  Zinc-dust  precipitation.  Eng.  &  Min.  Jour.,  Aug.  26, 
1911,  2  pp. 

MOULTON,  W.  A.  Cyanide  costs.  (Precipitation  and  clean-up  at  Liberty 
Bell.)  M.  &  S.  P.,  June  13,  1908.  "  More  Recent  Cyanide  Practice, "  p.  148. 

NEWMAN,  B.  Electrolytic  precipitation  of  gold  from  cyanide  solution. 
Electrochem.  &  Met.  Ind.,  Aug.,  1906,  4  pp. 

PACKARD,  G.  A.  Gold  precipitation  by  zinc  dust.  Proc.  Ch.  &  Met.  Soc., 
S.  A.,  vol.  3,  1902,  2  pp. 


CLASSIFIED  BIBLIOGRAPHY  241 

PARKS,  J.  R.     Electro-cyanide  process.     Min.  World,  Jan.  23,  1909,  2  pp. 

PARSONS,  A.  R.  Cyanide  costs.^  (Precipitation  and  clean-up  at  Deseret 
mill.)  M.  &  S.  P.,  July  11,  1908.  "More  Recent  Cyanide  Practice, "  p.  149. 

PHILLIPS,  F.  D.  Notes  on  precipitation.  Jour.  Ch.,  Met.,  &  Min.  Soc., 
S.  A.,  July  and  Dec.,  1910,  2  pp.;  abstracts  in  Mex.  Min.  Jour.,  Nov.,  1910; 
Min.  World,  Sept.  17,  1910;  Pac.  Miner,  Nov.,  1910. 

PRISTER,  A.  White  precipitate  of  precipitating  boxes  in  cyanide  works. 
Jour.  Ch.,  Met.,  &  Min.  Soc.,  S.  A.,  vol.  5,  1904,  pp.  62,  75,  129,  148,  and  171; 
abstract  in  Eng.  &  Min.  Jour.,  Dec.  22,  1904,  1  p. 

RHINERT,  J.  T.     Increasing  capacity  of  zinc  lathes.     Pac.  Miner,  Apr., 
1911,  1  p. 

RHODES,  C.  E.  Cyanide  costs.  (Precipitation  and  clean-up  at  Guana- 
juato.) M.  &  S.  P.,  Oct.  17,  1908.  "More  Recent  Cyanide  Practice," 
p.  150. 

RICE,  C.  T.  Improved  zinc-dust  feeder.  Eng.  &  Min.  Jour.,  Feb.  18, 
1911,  1  p. 

RICHMOND,  C.  P.  Electrolytic  precipitation  of  cyanide  solution.  (At 
Salvador,  Cent.  Amer.)  Eng.  &  Min.  Jour.,  Mar.  16,  1907,  3  pp. 

SHARWOOD,  W.  J.  Precipitation  of  gold  and  silver  from  cyanide  solution. 
Eng.  &  Min.  Jour.,  Apr.  20  and  May  18,  1905;  M.  &  S.  P.,  Apr.  29  to  May  13, 
1905,  3  pp. ;  abstract  from  Trans.  Calif.  Miners'  Assn. 

Precipitation  of  cyanide  solution.  (Zinc  dust.)  Eng.  &  Min.  Jour.,  June 
15,  1905,  1  p. 

SMITH,  M.  Notes  on  precipitation.  Jour.  Ch.,  Met.,  &  Min.  Soc.,  S.  A., 
Mar.,  1909,  2  pp.;  Apr.,  1909,  1  p.;  abstract  in  Min.  World,  June  5,  1909,  1  p. 

TIPPETT,  J.  M.  Cyanide  precipitation  and  clean-up  at  Portland  mill, 
Colo.  West.  Ch.  &  Met.,  Jan.,  1908,  3  pp. 

VIRGOE,  W.  H.  Consumption  of  zinc  in  cyanide  plants.  Nature,  cause, 
and  effect.  Jour.  Ch.,  Met.,  &  Min.  Soc.,  S.  A.,  Aug.,  1903,  12  pp.;  Dec., 
1903,  1  p.;  abstract  in  Eng.  &  Min.  Jour.,  Nov.  28,  1903,  2  pp.;  abstract  in 
M.  &  S.  P.,  Oct.  31  to  Nov.  21,  1903,  4  pp. 

VON  GERNET,  A.  Electrical  precipitation  of  gold.  Proc.  Ch.  &  Met. 
Soc.,  S.  A.,  vol.  1,  1895,  6  pp. 

VON  OETTINGEN,  A.  Theory  of  disassociation  as  applied  to  galvanic 
currents.  Proc.  Ch.  &  Met.  Soc.,  S.  A.,  vol.  2,  1899,  14  pp. 

WHEATLEY,  R.  L.  New  style  of  zinc  box.  Pac.  Miner,  June- July,  1911, 
2pp. 

WHITBY,  A.  Solutions  carrying  dissolved  gold.  Min.  World,  Aug.  6, 
1910,  1  p.;  abstract  from  Jour.  Ch.,  Met.,  &  Min.  Soc.,  S.  A. 

WILDE,  P.  DE.  Precipitating  gold  by  means  of  copper  salts.  Proc.  Ch.  & 
Met.  Soc.,  S.  A.,  vol.  2,  1898,  5  pp. 

WILDE  (P.  DE)  and  BETTEL  (W.).  Chemical  precipitation  of  gold.  Proc. 
Ch.  &  Met.  Soc.,  S.  A.,  vol.  2,  1898,  8  pp. 

WILLIAMS,  S.  H.  Wood  absorption  of  goki  solution.  Eng.  &  Min.  Jour., 
Sept.  9,  1905;  abstract  from  Inst.  Min.  &  Met. 

WILLIS,  H.  T.  Cause  of  short  zinc.  M.  &  S.  P.,  May  8,  1909.  "More 
Recent  Cyanide  Practice,"  p.  274. 

WITTEVEEN,  G.     Notes  on  De  Wilde  process  of  precipitating  gold  and 


242          TEXT  BOOK  OF  CYANIDE  PRACTICE 

silver  from  cyanide  solution.     Trans.  Mex.  Inst.,  Apr.,  1910,  6  pp.;  abstract 
in  Pac.  Miner,  Jan.,  1911,  1  p. 

YAGER,  A.  J.  Modification  of  Pachuca-tank  practice.  (Also  concerning 
zinc-dust  precipitation.)  M.  &  S.  P.,  Oct.  22,  1910,  1  p.;  abstract  in  Pac. 
Miner,  Nov.,  1910,  1  p. 

Australian  Mining  Standard.  Electro-cyanide  processes.  July  8,  1908, 
Ip. 

Engineering  and  Mining  Journal.  Electrical  precipitation  from  cyanide 
solutions.  Mar.  19,  1910. 

Screen  trays  for  zinc  boxes.     (For  holding  short  zinc.)     Nov.  13,  1909. 

Journal  Chemical,  Metallurgical,  and  Mining  Society,  S.  A.  Precipitation 
of  gold  from  solutions  by  carbonaceous  matter.  (A  discussion.)  Apr.,  1909, 
3pp.;  May,  1909,  1  p. 

Mining  and  Scientific  Press.  Charcoal  precipitation  from  cyanide  solution. 
Sept.  1,  1900,  1  p.;  Feb.  2,  1901;  Sept.  23,  1905. 

Electrolytic  precipitation  from  cyanide  solution.     Nov.  10,  1894,  1  p. 

Mining  World.  Solution  carrying  gold  and  silver.  Feb.  5,  1910,  1  p.; 
abstract  in  Jour.  Ch.,  Met.,  &  Min.  Soc.,  S.  A. 

0.     Cleaning-up,  Refining,  and  Melting 

AARONS  (J.  B.)  and  BLACK  (H.).  High  grade  bullion  from  zinc-box  pre- 
cipitates. Jour.  W.  A.  Cham.  Mines,  Aug.,  1911;  abstract  in  Min.  &  Eng. 
World,  Nov.  11,  1911. 

BROWN,  R.  G.  Note  on  treatment  of  zinc-box  precipitate  from  cyanide 
process.  Inst.  Min.  &  Met.,  vol.  4,  1896,  11  pp. 

BULLOCK,  L.  N.  B.  Cyanidation  at  Copala,  Mex.  (Clean-up,  melting, 
etc.)  M.  &  S.  P.,  Mar.  14,  1907,  1  p.  "Recent  Cyanide  Practice,"  p.  231. 

BURNETT,  D.  V.  Some  future  appliances  for  cyanide  clean-up.  (Washing 
trommel.)  Jour.  Ch.,  Met.,  &  Min.  Soc.,  S.  A.,  vol.  5,  p.  145,  1  p.;  abstract 
in  Eng.  &  Min.  Jour.,  May  18,  1905,  1  p. 

CALDECOTT  (W.  A.)  and  JOHNSON  (E.  H.).  Smelting  and  refining  of  gold 
zinc  slime.  Proc.  Ch.  &  Met.  Soc.,  S.  A.,  vol.  3,  1902,  18  pp. 

CAMPBELL  (B.  P.).  Refining  zinc-box  precipitate  with  sulphurous  acid. 
Pac.  Miner,  June,  1910. 

CLARKE,  D.  Gold  refining.  Aust.  Min.  Stand.,  series  of  articles  ending 
Jan.  22,  1908.  See  "Gold  Refining,"  by  Clarke. 

CLEVENGER,  G.  H.  Refining  of  precipitate  obtained  by  means  of  zinc  in 
cyanide  process.  T.  A.  I.  M.  E.,  vol.  34,  1903,  26  pp. 

COLLIE,  J.  E.     Matte  refining.     Pac.  Miner,  Mar.,  1910,  1  p. 

COOLIDGE,  R.  F.  Cupellation  of  lead  bullion.  (Zinc  precipitate.)  Eng. 
&  Min.  Jour.,  Oct.  14,  1911,  2  pp. 

CULLEN  (W.)  and  AYERS  (G.  F.).  Method  for  recovery  of  zinc  from 
solutions  of  sulphate.  Jour.  Ch.,  Met.,  &  Min.  Soc.,  S.  A.,  Sept.,  1909,  3  pp.; 
abstract  in  Min.  World,  Dec.  11,  1909,  2  pp. 

DONALDSON,  T.  Specific  gravity  of  bisulphate  solutions  for  dissolving 
zinc  shavings.  Jour.  Ch.,  Met.,  &  Min.  Soc.,  S.  A.,  Sept.,  1909;  abstract  in 
Min.  World,  Dec.  25,  1909,  1  p. 


CLASSIFIED  BIBLIOGRAPHY  243 

DRUCKER,  A.  E.  Treatment  of  matte  from  cyanide  mill.  M.  &  S.  P., 
May  18,  1907,  1  p.  "Recent  Cyanide  Practice,"  p.  260. 

HAMILTON,  E.  M.  Comparative  tests  between  coke  and  crude  oil  for 
melting  precipitate.  M.  &  S.  P.,  Nov.  24,  1906,  1  p.  "Recent  Cyanide 
Practice,"  p.  164. 

HEADDEX,  W.  P.  Some  mattes  formed  in  melting  zinc-box  precipitate. 
Their  composition  and  what  it  suggests.  Proc.  Colo.  Sci.  Soc.,  Dec.,  1907. 

HUBBARD,  J.  D.  Slag  reduction.  (From  precipitate  melting.)  M.&S.  P., 
Feb.  5,  1910,  1  p. 

HUNT,  B.  Refining  zinc-box  precipitate  with  sulphurous  acid.  Pac. 
Miner,  July,  1910. 

JOHNSON,  E.  H.  Reduction  of  zinc-gold  slime.  Proc.  Ch.  &  Met.  Soc., 
S.  A.,  vol.  2,  1897,  3  pp. 

LEE  (C.  W.)  and  BRUNTON  (W.  O.).  Notes  on  refining  of  base  bullion. 
Jour.  Ch.,  Met.,  &  Min.  Soc.,  S.  A.,  May,  1907,  2  pp.;  Aug.,  1907,  1  p.;  Oct., 
1907. 

MARTIN,  A.  H.  Some  methods  of  cleaning-up  a  cyanide  plant.  Ores  & 
Metals,  Aug.  20,  1907. 

MELVILL,  G.  Few  notes  on  cupeling  gold-lead  bullion.  Jour.  Ch.,  Met., 
&  Min.  Soc.,  S.  A.,  Nov.,  1908,  2  pp.;  Apr.,  1909. 

MEYER,  C.  E.  Proposed  process  for  treatment  of  zinc-gold  slime  before 
smelting.  Jour.  Ch.,  Met.,  &  Min.  Soc.,  S.  A.,  June,  1906,  3  pp.;  Sept.,  1906, 
Nov.,  1906,  1  p. 

Fluxing  of  gold  slime.  Jour.  Ch.,  Met.,  &  Min.  Soc.,  S.  A.,  ending  July, 
1905. 

MORRIS,  C.  J.  Production  of  high  grade  gold  bullion  from  zinc-box  pre- 
cipitate. Inst.  Min.  &  Met.,  vol.  15,  1906,  7  pp. 

NEAL,  W.  Treatment  of  gold  and  silver  precipitate  at  Dos  Estrellas, 
Mex.  M.  &  S.  P.,  Feb.  27,  1909,  1  p.  "More  Recent  Cyanide  Practice," 
p.  248. 

PIDDINGTON,  F.  L.  Notes  on  smelting  and  cupellation  of  cyanide  pre- 
cipitate, jewelers'  sweeps,  etc.  Jour.  Ch.,  Met.,  &  Min.  Soc.,  S.  A.,  Dec., 
1903,  May,  1904,  9  pp.;  June,  1904,  1  p. 

ROSE,  T.  K.  Refining  gold  bullion  and  cyanide  precipitate  with  oxygen 
gas.  Inst.  Min.  &  Met.,  1905,  vol.  14,  52  pp.;  abstract  in  Eng.  &  Min.  Jour., 
July  22,  1905,  2  pp. 

RUSDEN,  H.  Bag  house  experiment  with  Travener  process.  Eng.  &  Min. 
Jour.,  Oct.  14,  1905. 

SEWELL,  F.  W.  Refining  gold  and  silver  precipitate.  Mex.  Min.  Jour., 
Nov.,  1909,  2  pp.;  Min.  Sci.,  Dec.  9,  1909,  1  p. 

SMITH,  L.  Vacuum  filter  for  zinc-box  slime.  Eng.  &  Min.  Jour.,  Nov.  5, 
1910. 

STOCKHAUSEN,  F.  Liquation  in  cyanide  bars.  Proc.  Ch.  &  Met.  Soc., 
S.  A.,  vol.  2,  1897,  8  pp. 

SWEETLAND,  E.  J.  Quicksilver  recovered  in  cyanide  process.  M.  &  S.  P., 
May  21,  19O4. 

SWINNEY,  L.  A.  E.  Travener  process.  Inst.  Min.  &  Met.,  vol.  16,  1906, 
21pp. 


244  TEXT  BOOK  OF  CYANIDE  PRACTICE 

THOMAS,  A.  Battery  and  cyanide  gold  smelting.  Jour.  Ch.,  Met.,  &  Min. 
Soc.,  S.  A.,  July  to  Dec.,  1908,  10  pp. 

THOMAS,  J.  E.  Cyanide  works  clean-up  practice.  Jour.  Ch.,  Met.,  & 
Min.  Soc.,  S.  A.,  Oct.,  1906,  to  Feb.,  1907,  6  pp.;  abstract  in  M*.  &  S.  P.,  Jan.  12, 
1907,  1  p.  "Recent  Cyanide  Practice, "  p.  210. 

Some  improvements  in  cyanide  works  clean-up  appliances.  (Washing 
trommel.)  Jour.  Ch.,  Met.,  &  Min.  Soc.,  S.  A.,  Oct.,  1903,  1  p.;  Mar.,  1904, 
1  p.;  abstract  in  Eng.  &  Min.  Jour.,  Dec.  24,  1903. 

THOMAS  (J.  E.)  and  WILLIAMS  (G.  W.).  Use  of  bisulphate  of  sodium  in  the 
clean-up.  Jour.  Ch.,  Met.,  &  Min.  Soc.,  S.  A.,  vol.  5,  p.  334,  3  pp.;  vol.  6, 
p.  156,  2  pp.;  Sept.  to  Nov.,  1905,  5  pp. 

TRAVENER,  P.  S.  Lead  smelting  of  zinc-gold  slime.  Proc.  Ch.  &  Met. 
Soc.,  S.  A.,  vol.  3,  1902,  46  pp.;  Eng.  &  Min.  Jour.,  Jan.  31  and  Apr.  11,  1903, 

3pp. 

TRUSCOTT  (S.  J.)  and  YATES  (A.).  Treatment  of  precipitate  and  manip- 
ulation of  tilting  furnace  in  Sumatra.  Inst.  Min.  &  Met.,  vol.  16,  1906,  9  pp. 

WILLIAMS,  G.  W.  Notes  on  lime,  clean-up,  etc.  Jour.  Ch.,  Met.,  &  Min. 
Soc.,  S.  A.,  July  to  Sept.,  1905,  7  pp. 

WILMOUTH,  L.  J.  Experiments  on  the  assay  of  acid  washes  resulting  from 
cyanide  clean-up  by  use  of  bisulphate  of  sodium.  Jour.  Ch.,  Met.,  &  Min. 
Soc.,  S.  A.,  Oct.,  1909,  3  pp. 

WINGATE,  H.  Notes  on  treatment  of  zinc  precipitate  in  New  Zealand. 
T.  A.  I.  M.  E.,  vol.  33,  1902,  2  pp.;  abstract  in  M.  &  S.  P.,  Oct.  18,  1902,  1  p. 

YATES,  A.  Smelting  of  gold  precipitate  and  bullion  with  fuel  oil.  Jour. 
Ch.,  Met.,  &  Min.  Soc.,  S.  A.,  June,  1909,  2  pp.;  abstract  in  Eng.  &  Min. 
;  Jour.,  Sept.  4,  1909,  1  p.;  abstract  in  Min.  World,  Oct.  23,  1909,  1  p. 

ZACHERT,  V.  Precipitation  by  a  zinc-sodium  alloy.  Pac.  Miner,  Jan., 
1911. 

Pacific  Miner.     Preparation  of  sulphurous  acid.     July,  1910. 

P.    Telluride  Ore,  Roasting,  Bromocyanide,  and  Chlorination 

ARGALL,  P.  Chlorination  v.  cyaniding.  Eng.  &  Min.  Jour.,  Nov.  24, 
Dec.  15  and  29,  1904;  Jan.  12  and  19,  Feb.  16,  1905. 

Cyanidation  of  Cripple  Creek  ores.  (An  address.)  M.  &  S.  P.,  Dec.  24, 
1910,  2  pp. 

Cyaniding  sulphotelluride  ores.     Eng.  &  Min.  Jour.,  July  11,  1903,  1  p. 

Diehl  process.     Eng.  &  Min.  Jour.,  Oct.  31,  1903,  1  p. 

BARKER,  F.  L.  Cyaniding  Cripple  Creek  ores.  Mines  &  Mins.,  Apr.  and 
May,  1908,  5  pp. 

BRINSDEN,  F.  C.  Roasting  sulphotelluride  gold  ore  at  Kalgoorlie.  Proc. 
Aust.  Inst.  Min.  Engrs.,  Mar.,  1910,  15  pp. 

BROCKUNIER,  S.  H.  Experiments  with  bromocyanogen  on  southern  (U.  S.) 
gold  ores.  T.  A.  I.  M.  E.,  vol.  31,  1900,  5  pp.;  M.  &  S.  P.,  Apr.  26,  1902,  1  p. 

BROWN,  P.  Richardson  mine.  (Bromocyanide  process.)  Can.  Min. 
Jour.,  June  15,  1907,  4  pp. 

CHARLETON,  A.  G.  See  book,  "Gold  Mining  and  Milling  in  Western 
Australia,  etc." 


CLASSIFIED   BIBLIOGRAPHY  245 

CLARK,  D.     See  book,  "Australian  Mining  and  Metallurgy." 

CRANE,  W.  R.  Bibliography  of  roasting  ores,  furnaces,  etc.  In  "Index 
of  Mining  Engineering  Literature,'  by  Crane,  1909,  3  pp. 

CROWE,  T.  B.  Researches  upon  Cripple  Creek  telluride  ores.  Jour.  Ch., 
Met.,  &  Min.  Soc.,  S.  A.,  May  and  June,  1909,  4  pp.;  abstract  in  M.  &  S.  P., 
Sept.  25,  1909,  2  pp.  %  "More  Recent  Cyanide  Practice,"  p.  312. 

DAVIS,  W.  M.  Roasting  sulphotelluride  ores  for  cyanidation.  Min.  Sci., 
Mar.  2,  1911,  2  pp. 

EDWARDS,  J.  E.  Adaptation  of  Edwards  ore  roasting  furnace  to  cyanide 
practice.  Mex.  Min.  Jour.,  Aug.,  1910,  4  pp. 

FURMAN,  H.  VAN  F.  Roasting  gold  ores.  Mines  &  Mins.,  vol.  18,  pp.  416, 
442,  and  506,  5  pp. 

HUNT,  B.  Researches  upon  Cripple  Creek  telluride  ores.  M.  &  S.  P., 
Jan.  15,  1910.  "More  Recent  Cyanide  Practice,"  p.  316. 

JAMES,  A.  Notes  on  treatment  of  Kalgoorlie  sulphotelluride  ores.  Inst. 
Min.  &  Met.,  vol.  8,  1900,  34  pp. 

KNUTSEN,  H.     Diehl  process.     Inst.  Min.  &  Met.,  vol.  12,  1902,  36  pp. 

MACGREGOR,  W.  Roasting  previous  to  cyaniding.  Eng.  &  Min.  Jour., 
vol.  64,  p.  187,  1  p. 

MACK  (R.  L.),  SCIBIRD  (G.  H.),  and  READ  (T.  T.).  Roasting  of  telluride 
ore.  M.  &  S.  P.,  Dec.  14,  1907,  9  pp.  "More  Recent  Cyanide  Practice," 
p.  84. 

MARRINER,  J.  T.  Roasting  and  filter  press  treatment  at  Kalgoorlie.  Eng. 
&  Min.  Jour.,  Sept.  5,  1903,  2  pp. 

MULOLLAND,  C.  A.  Bromocyanide  process  for  gold  extraction.  Eng.  & 
Min.  Jour.,  vol.  59,  p.  510. 

NARDIN,  E.  W.  Bromocyaniding  of  gold  ores.  M.  &  S.  P.,  Oct.  24,  1908, 
3  pp.  "More  Recent  Cyanide  Practice,"  p.  226. 

PRICHARD  (W.  A.)  and  HOOVER  (H.  C.).  Treatment  of  sulphotelluride 
ores  at  Kalgoorlie.  Eng.  &  Min.  Jour.,  Aug.  1,  1903,  1  p. 

READ,  T.  T.  Cripple  Creek  metallurgy.  M.  &  S.  P.,  Feb.  18,  1911, 
lp. 

SCHNEIDER,  E.  A.  Cyanidation  v.  chlorination.  Eng.  &  Min.  Jour., 
vol.  59,  p.  461. 

SIMPSON,  W.  E.  Treatment  of  telluride  ores  by  dry-crushing  and  roasting 
for  cyanidation  at  Kalgoorlie.  Inst.  Min.  &  Met.,  vol.  13,  1903,  39  pp.; 
abstract  in  M.  &  S.  P.,  Dec.  5  to  26,  1903,  4  pp. 

VON  BERNEWITZ,  M.  W.  Cyanide  notes  on  bromocyanide  process.  M.  & 
S.  P.,  May  7,  1910.  "More  Recent  Cyanide  Practice, "  p.  316. 

Roasting  at  Kalgoorlie.     M.  &  S.  P.,  May  13,  1911,  2  pp. 

WALCOTT,  G.  E.  Cyanidation  at  Cripple  Creek.  Eng.  &  Min.  Jour., 
vol.  79,  p.  1087,  1  p. 

WORCESTER,  S.  A.  Milling  in  Cripple  Creek  district.  Eng.  &  Min.  Jour., 
May  8,  1909,  2  pp. 

WORRELL,  S.  H.  Chemistry  of  bromocyanogen  process.  M.  &  S.  P., 
Mar.  6,  1909,  1  p.  "More  Recent  Cyanide  Practice,"  p.  250. 

Metallurgical  and  Chemical  Engineer.  Notes  on  Cripple  Creek  mill  prac- 
tice, Apr.,  1911,  3  pp. 


246          TEXT  BOOK  OF  CYANIDE  PRACTICE 

Mining  and  Scientific  Press.  Bromocyanogen  process  at  Deloro,  Canada. 
Sept.  21,  1901. 

Cyanidation  and  chlorination  in  Colorado.     Vol.  76,  p.  538. 
Ore  treatment  —  cyanide  or  chlorine.     Vol.  72,  p.  25,  1  p. 
Roasting  at  Kalgoorlie.     July  9,  1910. 

Q.    Cupriferous  Ore  and  Solution 

ANDERSON,  I.  Regenerating  copper  cyanide  solution.  M.  &  S.  P.,  Feb. 
5  and  May  28,  1910.  "More  Recent  Cyanide  Practice, "  pp.  352  and  355. 

ARENTS,  C.  A.  Copper  in  cyanide  solutions.  M.  &  S.  P.,  Oct.  6,  1906. 
"Recent  Cyanide  Practice,"  p.  132. 

BARKER,  H.  A.  Notes  on  cupriferous  cyanide  solutions.  Inst.  Min.  & 
Met.,  vol.  12,  1903,  5  pp. 

BRERETON,  E.  L.  G.  Ammonia-copper  cyanide  process.  Inst.  Min.  & 
Met.,  vol.  15,  1906,  12  pp.;  vol.  16,  1907,  5  pp. 

BRERETON  (E.  L.  G.)  and  JARMAN  (A.).  Laboratory  experiments  upon 
use  of  ammonia  and  its  compounds  in  cyaniding  cupriferous  ores  and  tailing. 
Inst.  Min.  &  Met.,  vol.  14,  1905,  45  pp.;  abstract  in  Eng.  &  Min.  Jour.,  Apr. 
27  and  June  22,  1905,  4  pp. 

BROWN,  W.  S.  Cyanide  treatment  of  cupriferous  tailing  by  sulphuric  acid 
process.  Inst.  Min.  &  Met.,  vol.  15,  1906,  7  pp. 

BROWNE,  R.  S.  Precipitation  of  coppery  cyanide  solutions.  M.  &  S.  P., 
Jan.  24,  1903,  1  p. 

CHANDLER,  E.  D.  Copper  in  cyanide  solutions.  M.  &  S.  P.,  Sept.  1  and 
Nov.  3,  1906,  1  p.  "Recent  Cyanide  Practice,"  p.  161. 

EISSLER,  M.     "Hydro-metallurgy  of  copper."     1904. 

GREEN,  L.  M.  Double  cyanides  of  copper.  Eng.  &  Min.  Jour.,  Nov.  18, 
1905,  1  p. 

JANIN,  L.  Cyaniding  of  cupriferous  ores.  Eng.  &  Min.  Jour.,  Aug.  17, 
1901,  1  p. 

Treatment  of  cupriferous  gold  ores  by  cyanide.  Eng.  &  Min.  Jour.,  Dec. 
20,  1902,  1  p. 

McCAUGHEY,  W.  J.  Solvent  effect  of  cupric  and  ferric  salt  solutions  upon 
gold.  Jour.  Am.  Chem.  Soc.,  Dec.,  1909,  10  pp. 

MOSHER,  D.  Ammonia-cyanidation  and  complex  zinc  problem.  Mex. 
Min.  Jour.,  Aug.,  1910,  5  pp. 

Ammonia-cyanide  process.     Pac.  Miner,  Mar.,  1910,  4  pp. 

SULMAN,  H.  L.  Note  on  ammonia  copper  cyanide  process.  Inst.  Min.  & 
Met.,  vol.  14,  1905,  14  pp. 

TREADWELL,  F.  P.  Potassium  copper  cyanide.  Eng.  &  Min.  Jour.,  July 
28,  1904. 

WHEELOCK,  R.  P.  Tests  on  acid  regeneration  of  copper  cyanide  solution. 
M.  &  S.  P.,  Dec.  18,  1909,  and  Mar.  12,  1910,  6  pp.  "More  Recent  Cyanide 
Practice,  "pp.  341  and  352. 

VIRGOE,  W.  H.  Titration,  use,  and  precipitation  of  cyanide  solution  con- 
taining copper.  Inst.  Min.  &  Met.,  vol.  10,  1901,  40  pp. 

Chemistry  of  copper  cyanides.     Eng.  &  Min.  Jour.,  May  19,  1904,  1  p. 


CLASSIFIED  BIBLIOGRAPHY  247 

YEANDLE,  W.  H.  Cyanidation  of  copper-gold  tailing.  Eng.  &  Min. 
Jour.,  May  19,  1904. 

Mining  and  Scientific  Press.  Cyaniding  copper-bearing  gold  ores.  May 
20,  1905,  1  p. 

Leaching  low-grade  copper  ores.     Vol.  87,  p.  169,  1  p. 

R.     Concentrate  Cyanidation 

BANKS,  E.  G.     Cyanidation  of  concentrate.     M.  &  S.  P.,  Jan.  21,  1911. 

Cyaniding  concentrate  at  Waihi.  Min.  <&  Eng.  Rev.,  Mar.  6,  1911;  ab- 
stract in  Eng.  &  Min.  Jour.,  Aug.  5,  1911. 

BROWN,  F.  C.  Cyanidation  of  concentrate.  M.  &  S.  P.,  Aug.  27,  1910, 
Ip. 

CHRISTY,  S.  B.  Cyaniding  gold-bearing  sulphurets.  M.  &  S.  P.,  Apr.  2 
to  23,  1904,  4  pp.;  abstract  from  Trans.  Calif.  Miners'  Assn. 

COLEMAN,  M.  N.     Cyanidation  of  sulphide.     M.  &  S.  P.,  Sept.  3,  1910,  2  pp. 

CROSSE,  A.  F.  Treatment  of  pyritic  concentrate  by  cyanide  process. 
Proc.  Ch.  &  Met.  Soc.,  S.  A.,  vol.  1,  1895,  5  pp.;  Eng.  &  Min.  Jour.,  vol.  59, 
p.  559. 

Concentrate  and  blacksand  treatment.    S.  A.  Min.  Jour.,  May  27, 1911, 1  p. 

DENNY,  H.  S.  Treatment  of  concentrate  on  the  Rand.  Eng.  &  Min. 
Jour.,  Sept.  26,  1903,  3  pp. 

DRUCKER,  A.  E.  Cyanidation  of  concentrate.  M.  &  S.  P.,  Mar.  19, 
1910,  2  pp.  "More  Recent  Cyanide  Practice,"  p.  384. 

Treatment  of  a  concentrate  slime.  M.  &  S.  P.,  Apr.  4,  1908,  2  pp.  "More 
Recent  Cyanide  Practice,"  p.  190. 

Tube-milling  in  Korea.  (Cyanidation  of  concentrate.)  M.  &  S.  P.,  Sept. 
22,  1906,  2  pp.  "Recent  Cyanide  Practice,"  p.  110. 

ELWES,  H.  G.  Cyanidation  of  argentiferous  concentrate.  Eng.  &  Min. 
Jour.,  July  22,  1905,  1  p. 

EVANS,  G.  C.     Cyanidation  of  concentrate.     M.  &  S.  P.,  Dec.  24,  1910. 

FULTON,  T.  T.  Lixiviation  of  an  auriferous  arsenopyrite  concentrate  by 
cyanide.  Jour.  Min.  Soc.  Nova  Scotia,  1907,  27  pp. 

GROTHE,  A.  Notes  on  cyanide  treatment  of  concentrate.  Eng.  &  Min. 
Jour.,  Oct.  2,  1902,  1  p. 

GODBE,  E.  L.  Cyaniding  sulphide  direct.  M.  &  S.  P.,  Apr.  16  and  23, 
1904. 

HARRISON,  R.  C.     Cyaniding  raw  pyrite.     M.  &  S.  P.,  Jan.  21,  1905,  1  p. 

HARTLEY,  Z.  B.  Some  observations  on  treatment  of  pyritic  concentrate 
by  cyanidation.  Pac.  Miner,  Nov.,  1910,  1  p.;  abstract  in  Mex.  Min.  Jour., 
Mar.,  1911,  1  p. 

HOBSON,  F.  J.  Cyanidation  of  concentrate.  M.  &  S.  P.,  Feb.  3,  1906,  1  p. 
"Recent  Cyanide  Practice,"  p.  22. 

HUBBARD,  J.  D.  Cyaniding  concentrate  at  Taracol,  Korea.  M.  &  S.  P., 
Oct.  2,  1909,  3  pp.  "More  Recent  Cyanide  Practice,"  p.  318. 

LASS,  W.  P.  Cyanide  plant  at  Treadwell  Mines,  Alaska.  (Concentrate 
treatment.)  Trans.  A.I.M.E.,  Oct.,  1911,  34  pp.;  abstract  in  M.  &  S.  P., 
Oct.  21,  1911,  7  pp. 


248          TEXT  BOOK  OF  CYANIDE  PRACTICE 

LINDSAY,  R.  Treatment  of  black  sand  concentrate  at  Geldenhuis  Deep 
mill.  S.  A.  Min.  Jour.,  July  22,  1911,  1  p.;  Min.  &  Eng.  World,  Oct.  14, 
1911,  1  p.  Abstract  from  Jour.  Ch.,  Met.,  &  Min.  Soc.,  S.  A.,  July,  1911, 
3pp. 

LODGE,  R.  W.  Cyanide  process  as  applied  to  the  concentration  from  a 
Nova  Scotia  gold  ore.  T.  A.  I.  M.  E.,  vol.  25,  1895,  4  pp.  See  "Notes  on 
Assaying,"  by  Lodge. 

MACDONALD,  B.  Cyanidation  of  concentrate.  Eng.  &  Min.  Jour.,  Dec. 
23  and  30,  1905,  4  pp. 

MEGRAW,  H.  A.  Notes  on  cyanidation  of  concentrate.  Min.  World, 
Aug.  13,  1910,  2  pp. 

PARSONS,  A.  B.  Cyanide  treatment  of  concentrates  at  Goldfield  Con- 
solidated, Nevada.  Eng.  &  Min.  Jour.,  Feb.  18,  1911,  2  pp. 

RECKNAGEL,  R.  Cyaniding  sulphide  ores.  Eng.  &  Min.  Jour.,  Nov.  13, 
1897,  2  pp. 

RICKARD,  T.  A.  Cyanidation  of  concentrate  at  Alaska-Tread  well.  Min. 
Mag.,  Oct.,  1910,  1  p. 

SMITH,  F.  C.  Cyanidation  of  raw  pyritic  concentrate.  T.  A.  I.  M.  E., 
vol.  37,  1906,  6  pp. 

STEPHENS,  F.  B.  Treatment  of  refractory  auriferous  sulphide  at  Cassilis 
mine,  Victoria.  M.  &  S.  P.,  June  24  and  July  1,  1905,  2  pp.;  abstract  from 
Inst.  Min.  &  Met. 

TAYS,  E.  A.  H.  Realizing  on  concentrate  when  shipping  is  impracticable. 
M.  &  S.  P.,  Feb.  8,  1902,  1  p. 

TREMOUREUX,  R.  E.  Successful  treatment  of  concentrate  by  cyanidation. 
Mex.  Min.  Jour.,  Nov.,  1910,  1  p. 

VAN  SUAN,  P.  E.  Cyaniding  at  Montgomery-Shoshone  mill.  (Including 
cyanidation  of  concentrate.)  Eng.  &  Min.  Jour.,  Jan.  22,  1910,  3  pp. 

VON  BERNEWITZ,  W.  M.  Treatment  of  concentrate  at  Kalgoorlie.  Min. 
Jour.,  May  21,  1910,  2  pp. 

WRIGHT,  C.  M.  P.  Cyaniding  concentrate  by  percolation  at  Choukpazat. 
Inst.  Min.  &  Met.,  vol.  12,  1902,  4  pp. 

Australian  Mining  Standard.     Treatment  of  concentrate.     Jan.  1,  1908. 

Mining  and  Scientific  Press.  Cyaniding  raw  sulphide.  Sept.  9,  1905; 
abstract  from  Jour.  Ch.,  Met.,  &  Min.  Soc.,  S.  A. 

Cyaniding  sulphide  gold  ores.     June  7,  1902,  1  p. 
Kalgoorlie,  Western  Australia.     (Concentrate  cyanidation.)     Mar.  6, 
1909,  p.  342,  1  p. 

S.     Other  Refractory  Ores 

ALDERSON,  M.  W.     Cyaniding  base  ore.     M.  &  S.  P.,  Feb.  4,  1899,  1  p. 

BETTEL,  W.  Nature  and  treatment  of  refractory  ores.  (Cyanidation.) 
S.  A.  Min.  Jour.,  Dec.  11,  1909,  3  pp.;  abstract  in  Min.  World,  Feb.  26,  1910, 
2pp. 

BRETT,  H.  T.  Metallurgy  at  Globe  and  Phoenix,  Rhodesia.  (Cyaniding 
antimonial  ores.)  Min.  Mag.,  July,  1911;  abstract  in  Min.  &  Met.  Jour., 
Sept.,  1911. . 


CLASSIFIED   BIBLIOGRAPHY  249 

BROWN,  E.  P.  Treatment  of  gold-bearing  antimony  ore.  M.  &  S.  P., 
June  9,  1906. 

BURNETT,  D.  V.  A  quick  treatment  by  cyanide  of  black  sands.  Jour. 
Ch.,  Met.,  &  Min.  Soc.,  S.  A.,  Feb.  to  May,  1906,  3  pp. 

CIRKEL,  F.  Treatment  problem  of  the  Republic,  Washington  ores.  Eng. 
&  Min.  Jour.,  Feb.  1,4908,  1  p. 

DAY  (D.  T.)  and  RICHARDS  (R.  H.).  Investigation  of  black  sands  from 
placer  mines.  Bull.  285,  U.  S.  Geol.  Survey,  p.  150,  15  pp. 

Useful  minerals  in  black  sands  of  Pacific  Slope,  with  bibliography  of  papers 
bearing  on  black  sands.  U.  S.  Geol.  Survey  —  Min.  Res.  of  U.  S.,  1905, 
p.  1175,  84  pp. 

Nothing  on  cyanidation  in  above. 

FRASER,  LEE.  A  cyanide  problem.  (Suggested  treatment  for  antimonial 
ores.)  M.  &  S.  P.,  Dec.  3,  1910. 

HAMILTON,  E.  M.  Cyanidation  of  manganese  silver  ores  in  Mexico.  M. 
&  S.  P.,  Dec.  4,  1909,  and  Feb.  5,  1910;  abstract  from  Jour.  Ch.,  Met.,  &  Min. 
Soc.,  S.  A. 

LAMB,  M.  R.  Treating  low  grade  refractory  ores  of  Mexico.  Min.  World, 
July  3,  1909,  3  pp. 

MASON,  F.  H.  Separation  of  gold  in  antimony  ores.  (Experiments.) 
M.  &  S.  P.,  Apr.  28,  1906,  2  pp. 

PROBERT,  F.  H.  Cyaniding  complex  gold  ores.  M.  &  S.  P.,  June  15,  1901, 
Ip. 

STEVENS,  F.  B.  Treatment  of  highly  acidic  tailing  by  cyanide.  M.  &  S.  P., 
June  14,  1902,  1  p. 

VON  BERNE WITZ,  M.  W.  Graphite  —  an  obstacle  to  good  cyaniding, 
M.  &  S.  P.,  Dec.  4,  1909,  Feb.  5  and  June  11,  1910,  2  pp.  "More  Recent 
Cyanide  Practice,"  p.  336. 

WILSON,  J.  K.  Notes  on  occurrence  and  treatment  of  an  auriferous  ore 
containing  insoluble  arsenides.  Jour.  Ch.,  Met.,  &  Min.  Soc.,  S.  A.,  Feb., 
1907,  4  pp. 

Mining  and  Scientific  Press.  A  cyanide  problem.  (Antimonial  ore.) 
Aug.  13,  1910. 

Mining  Science.     Cyanjflation  of  manganese-silver  ores.     Jan.  20,  1910. 

,/  T.     Cyanide  Poisoning 

V/BOYD,   F.   K.     Poisoning  of  animals  by  cyanide  solutions.     Mex.   Min. 
Jour.,  Jan.,  1911. 

^/BROWN,  H.  L.     Cyanide  poisoning.     (Of  cattle  by  cyanide  discharged.) 
Eng.  &  Min.  Jour.,  Nov.  3,  1906,  1  p. 

JENKINS,  H.  C.  First  aid  treatment  of  acute  cyanide  poisoning.  Inst. 
Min.  &  Met.,  vol.  13,  1904,  5  pp. 

I/JOHNSTON,  A.  M.     Experiment  in  cyanide  poisoning.     Proc.  Ch.  &  Met. 
Soc.,  S.  A.,  vol.  2,  1899,  9  pp. 

JONA,  J.  L.  Antidote  for  cyanide  poisoning.  Eng.  &  Min.  Jour.,  Sept.  30, 
1911. 

KENNEDY,  A.  P.    Cyanide  poisoning.    (Eczema.)     M.  &  S.  P.,  Mar.  9, 1907. 


250          TEXT  BOOK  OF  CYANIDE  PRACTICE 

MARTIN  (C.  J.)  and  O'BRIEN  (R.  A.).     Antidote  for  cyanide  poisoning. 
Eng.  &  Min.  Jour.,  Aug.  8,  1903,  1  p. 
^ROGERS,  A.  H.     Poisoning  by  cyanide.     Eng.  &  Min.  Jour.,  Dec.  3,  1910. 

WOODRUFF,  C.  H.  Cyanide  poisoning  and  antidotes.  Mex.  Min.  Jour., 
Aug.,  1910,  1  p. 

^x&ustralian  Mining  Standard.     Cyanide  poisoning.     Jan.  6,  1909,  1  p. 
^Engineering  and  Mining  Journal.     Poisoning  by  cyanide.     Nov.  26,  1910. 
^^Fburnal  Chemical,   Metallurgical,  and  Mining  Society,  S.  A.     Report  of 
committee  upon  cyanide  poisoning.     May,  1904,  3  pp. 

See  vol.  2  (Proc.  Ch.  &  Met.  Soc.,  S.  A.),  1897-1899,  generally. 

Mining  and  Scientific  Press.  Cyanide  poisoning.  Sept.  29,  1906,  1  p. 
"Recent  Cyanide  Practice,"  p.  123. 

Pacific  Miner.  Cyanide  poisoning.  Aug.,  1909,  2  pp.;  abstract  in  Mex. 
Min.  Jour.,  Jan.,  1910,  1  p. 

U.  Construction,  and  Pulp  and  Residue  Conveying  and  Disposal 

ADAMS,  H.  Disposal  of  residue  at  Kalgoorlie.  Proc.  Aust.  Inst.  Min. 
Engrs.,  July,  1909,  13  pp. 

BALDWIN,  C.  K.  Tailing  disposal  plant  at  Wolverine  mill.  Eng.  &  Min. 
Jour.,  July  10,  1909,  3  pp. 

BLUE,  T.  K.  Flow  of  water  carrying  sand  in  suspension.  Eng.  &  Min. 
Jour.,  Sept.  21,  1907,  4  pp. 

BOERICKE,  W.  F.  Tailing  elevators  for  dumps.  Eng.  &  Min.  Jour.,  Sept. 
23,  1911. 

BOERICKE  (W.  F.)  and  EASTMAN  (B.  L.).  Home-made  cyanide  plant. 
M.  &  S.  P.,  Nov.  21,  1908,  1  p.  ''More  Recent  Cyanide  Practice,"  p.  231. 

BOSQUI,  F.  L.  Iron  v.  wood  for  cyanide  leaching  tanks.  M.  &  S.  P., 
Apr.  14,  1906,  1  p.  "Recent  Cyanide  Practice,"  p.  39. 

BROWN,  A.  S.  Modern  cyaniding  practice  and  machinery.  Eng.  Mag., 
Sept.,  1909,  18  pp. 

BROWN,  R.  G.  Tailing  elevators.  Eng.  &  Min.  Jour.,  Apr.  14,  1904,  1  p. 
"Notes  on  Metallurgical  Mill  Construction." 

BROWNE,  R.  S.  Designing  of  a  sand  leaching  plant.  Pac.  Miner,  Aug. 
and  Sept.,  1910,  7  pp. 

Mechanical  equipment  of  cyanide  plants.     Pac.  Miner,  Sept.,  1909,  4  pp. 

How  to  set  up  wood  stave  tanks.     M.  &  S.  P.,  Aug.  22,  1905,  1  p. 

COLEMAN,  W.  N.  Cost  of  small  cyanide  plant.  Pac.  Miner,  Aug.,  1909, 
2pp. 

COLLINS,  E.  A.  Tailing  wheels  v.  pumps.  M.  &  S.  P.,  Oct.  31,  1908, 
2pp. 

CRANK,  A.  F.  Cyanide  sand  handling  at  Robinson  mine.  Min.  Jour., 
July  25,  1908,  1  p. 

CRANK  (A.  F.)  and  BUTTERS  (C.).  System  of  handling  sand  mechanically 
for  cyanide  vats.  Inst.  Min.  &  Met.,  vol.  13,  1903,  26  pp.;  abstract  in  Eng. 
&  Min.  Jour.,  Dec.  5,  1903,  2  pp. 

EGGERS,  J.  H.  Cyanide  plant  constructed  of  masonry.  Pac.  Miner, 
Jan.,  1911,  4  pp. 


CLASSIFIED   BIBLIOGRAPHY  251 

HERRICK,  R.  L.  Handling  (and  impounding)  tailing  at  Colorado  City. 
Mines  &  Mins.,  May,  1910,  4  pp. 

HUNTER,  CHAS.  Cheap  form  of  cyanide  plant.  Inst.  Min.  &  Met.,  vol. 
17,  1907,  7  pp. 

LOBO,  G.  Electricity  in  cyanide  plants.  Mex.  Min.  Jour.,  Aug.,  1910, 
3  pp. 

JARMAN,  A.  Silting  (of  rivers  by  tailing)  at  Waihi.  Min.  Mag.,  Sept., 
1910,  4  pp. 

JONES,  A.  H.    Tailing  wheels  v.  pumps.     M.  &  S.  P.,  Oct.  3,  1908. 

LAMB,  M.  R.  Variables  influencing  cyanide  plant  design.  Eng.  &  Min. 
Jour.,  July  2,  1910,  1  p.  • 

LASCHINGER  (E.  L.)  and  WOOD  (W.  H.).  Tailing  elevators.  Eng.  &  Min. 
Jour.,  Mar.  24  and  Apr.  14,  1904,  3  pp.  "Notes  on  Metallurgical  Mill  Con- 
struction." 

MACFARREN,  H.  W.  Impounding  mill  tailing.  M.  &  S.  P.,  Sept.  4,  1909, 
Ip. 

Tailing  disposal  at  Mercur,  Utah.     M.  &  S.  P.,  July  25,  1908,  1  p. 

MESS,  L.     Reinforced  concrete  tanks.     M.  &  S.  P.,  July  25,  1908,  1  p. 

MILL,  A.  R.  Air-lift  for  transporting  sand.  Pac.  Miner,  Mar.,  1911,  1  p.; 
Eng.  &  Min.  Jour.,  Apr.  8,  1911,  1  p. 

NEAL,  W.     Conical  bottom  tanks.     M.  &  S.  P.,  July  25,  1908. 

NICOL,  J.  M.  Dynamics  of  cyanide  process.  Mex.  Min.  Jour.,  Aug., 
1910,  6  pp. 

OVERSTROM,  G.  A.  Conveying  tailing  in  launders.  M.  &  S.  P.,  Sept.  14, 
1907,  1  p.  " Recent  Cyanide  Practice,"  p.  331. 

READ,  T.  T.     Sand  launders.     Eng.  &  Min.  Jour.,  Dec.  16,  1905,  1  p. 

REID,  W.  L.  Tailing  wheels  compared  with  centrifugal  pumps.  M.  & 
S.  P.,  Sept.  19,  1908,  1  p.  "Recent  Cyanide  Practice." 

RICE,  C.  T.  Sluicing  out  sand  tanks  at  Grass  Valley,  Calif.  Eng.  &  Min. 
Jour.,  Jan.  28,  1911. 

RICKETTS,  L.  D.  Tailing  dam  of  Cananea  Copper  Co.  Eng.  &  Min.  Jour., 
Mar.  5,  1909,  1  p. 

Rix,  R.  A.     Air-lift  pumping.     M.  &  S.  P.,  Oct.  15,  1910,  2  pp. 

SCHMITT,  C.  O.  Table  of  grades  for  launders  and  pipes  in  reduction  plants. 
Jour.  Ch.,  Met.,  &  Min.  Soc.,  S.  A.,  Jan.,  1909. 

SHAPLEY,  E.     Air-lifts  at  Santa  Natalia  mill.     Pac.  Miner,  Sept.,  1909 
IP- 
SMART,  E.     Plant  for  extraction  of  gold  by  cyanide  process.     Eng.  &  Min. 
Jour.,  vol.  60,  p.  417,  2  pp. 

STORMS,  W.  H.  Tailing  dams  and  conservation  of  mill  water.  Eng.  & 
Min.  Jour.,  Aug.  6,  1910,  2  pp. 

VAN  LAW,  C.  W.  Conveying  tailing  in  launders  and  pipes.  M.  &  S.  P., 
July  20  and  Oct.  12,  1907,  2  pp.  "Recent  Cyanide  Practice,  "  pp.  320  and  331. 

VON  BERNE WITZ,  M.  W.  Dumping  residues  at  Kalgoorlie.  M.  &  S.  P. 
Sept.  21,  1907,  2  pp. 

WEPPER,  G.  W.     Tailing  wheels  or  pumps.     M.  &  S.  P.,  Oct.  31,  1908,  1  p. 

WESTON,  E.  M.  Tailing  elevators  on  the  Rand.  Eng.  &  Min.  Jour. 
Sept.  12,  1908,  1  p. 


252          TEXT  BOOK  OF  CYANIDE  PRACTICE 

Description  of  cheap  cyanide  plant  erected  in  Western  Australia.  Jour. 
Ch.,  Met.,  &  Min.  Soc.,  S.  A.,  vol.  5,  p.  23,  1  p. 

Australian  Mining  and  Engineering  Review.  Sludge  problem  in  New 
Zealand.  (Tailing  in  rivers.)  Aug.  5,  1910,  3  pp. 

Engineering  and  Mining  Journal.  Blaisdell  apparatus  at  El  Oro.  Eng. 
&  Min.  Jour.,  vol.  83,  p.  230,  1  p. 

Conveying  at  El  Oro  mill.     (Launder  grade.)     Eng.  &  Min.  Jour., 
Apr.  4,  1908. 

Disposal  of  slime  and  tailing  at  Stella  mine,  N.  Y.     Eng.  &  Min.  Jour., 
Sept.  18,  1909,  1  p. 

Efficiency  of  air-lift  as  a  solution  pump.     Eng.  &  Min.  Jour.,  Aug.  7, 
1909. 

Jackson  method  of  tailing  disposal.     (Michigan  copper  mines.)     Eng. 
&  Min.  Jour.,  Mar.  28,  1908,  1  p. 

Engineering  News.  Handling  stamp-mill  tailing  by  belt  conveyors.  Oct. 
28,  1909,  2  pp. 

Metallurgical  and  Chemical  Engineer.  Cyanide  tailing  disposal  in  Mexico. 
Nov.,  1911,  2  pp. 

Mining  and  Scientific  Press.     Building  a  concrete  tank.     Mar.  3,  1906. 
Handling  residue  in  New  South  Wales.     Oct.  12,  1907,  1  p. 
Elevating  sand.     July  8,  1911,  1  p. 

Mining  World.  Sand  filling  (of  worked-out  stopes)  on  the  Rand.  Aug.  6, 
1910,  1  p. 

Pacific  Miner,     Method  of  erecting  wood  tanks.     Feb.,  1910,  1  p. 
South  African  Mining  Journal.     New  Rand  tailing  elevator.     Sept.  26, 
1908,  1  p. 

Sand  filling  (of  worked-out  stopes)  at  the  Simmer  and  Jack.     Sept. 
17,  1910. 

V.    Tube-Milling  and  Fine-Grinding 

ABBE,  R.  F.  First  tube  mill  in  metallurgy.  Eng.  &  Min.  Jour.,  May  26 
and  June  16,  1906,  1  p. 

ARGALL,  P.  Modern  crushing  and  grinding  machinery.  Eng.  &  Min. 
Jour.,  May  11,  1904,  2  pp.  "Notes  on  Metallurgical  Mill  Construction." 

BALL,  H.  S.  Economics  of  tube  milling.  Bull.  No.  83,  Inst.  Min.  &  Met., 
Aug.,  1911;  abstract  in  M.  &  S.  P.,  Sept.  23,  1911,  3  pp. 

BANKS,  E.  G.  Grinding  in  tube  mills  at  Waihi,  New  Zealand.  T.  A.  I. 
M.  E.,  vol.  38,  1907,  4  pp.;  Mines  &  Mins.,  vol.  27,  p.  492,  1  p.;  Min.  World, 
Apr.  6,  1907,  2  pp. 

BARRY,  H.  P.     Tube-mill  lining.     Aust.  Min.  Stand.,  Dec.  2,  1908,  1  p. 

Tube-mill  lining.  M.  &  S.  P.,  Mar.  30,  1907,  1  p.  "Recent  Cyanide 
Practice, "  p.  239. 

BELL,  J.  W.  Critical  moisture  in  tube  mill  feed.  Min.  Mag.,  Apr.,  1911, 
Ip. 

BELL  (J.  W.)  and  QUARTANO  (A.).  Critical  moisture  in  tube-mill  feed. 
Min.  Mag.,  Sept.,  1911,  2  pp. 

BOSQUI,  F.  L.  Fine-grinding.  M.  &  S.  P.,  Feb.  3  and  10,  1906,  2  pp. 
"Recent  Cyanide  Practice,"  p.  25, 


CLASSIFIED  BIBLIOGRAPHY  253 

Boss,  M.  P.  Fine-grinding.  M.  &  S.  P.,  Feb.  17,  1906,  1  p.  "Recent 
Cyanide  Practice,"  p.  31. 

BRADLEY,  W.  W.  Tube-mill  lining.  M.  &  S.  P.,  Jan.  5,  1907,  1  p.  "Re- 
cent Cyanide  Practice,"  p.  207. 

BRETT,  H.  T.  Cyanide  practice  at  Kalgoorlie,  (Tube  mills  v.  pans.) 
M.  &  S.  P.,  Dec.  22,  1906,  2  pp.  "Recent  Cyanide  Practice,"  p.  189. 

BROWN,  F.  C.  Importance  of  fine-grinding  in  cyanide  treatment  of  gold 
and  silver  ores.  T.  A.  I.  M.  E.,  vol.  36,  1905,  7  pp. 

BROWN,  J.  R.     El  Oro  tube-mill  lining.     (Patents.)     M.  &  S.  P.,  Feb.  29, 

1908,  1  p.     "More  Recent  Cyanide  Practice,"  p.  120. 

BUTTER,  C.  Notes  on  tube-milling  at  El  Oro,  Mex.  M.  &  S.  P.,  May  26, 
1906,  1  p.  "Recent  Cyanide  Practice,"  p.  55. 

BUTTERS  (C.)  and  HAMILTON  (E.  M.).  On  cyaniding  of  ore  at  El  Oro, 
Mex.  Dealing  principally  with  regrinding  of  sand.  Inst.  Min.  &  Met., 
vol.  14,  1904,  44  pp.;  abstract  in  Eng.  &  Min.  Jour.,  Dec.  15,  1904,  1  p. 

CAETANI  (G.)  and  BURT  (E.).  Fine-grinding  of  ore  by  tube  mills,  and 
cyaniding  at  El  Oro,  Mex.  T.  A.  I.  M.  E.,  vol.  37,  1906,  53  pp. 

CALDECOTT  (W.  A.)  and  PEARCE  (S.  H.).  Computation  of  crushing  effi- 
ciency of  tube  mills.  Jour.  Ch.,  Met.,  &  Min.  Soc.,  S.  A.,  Sept.,  1906,  2  pp.; 
Jan.  to  Mar.,  1907,  7  pp. 

CHAPMAN,  R.  W.  Calculation  of  comparative  efficiencies  of  crushing  and 
grinding  machines.  Proc.  Aust.  Inst.  Min.  Engrs.,  Oct.,  1909,  5  pp. 

CLARKE,  R.  Pans  v.  tube  mills.  (Comparative  test.)  M.  &  S.  P., 
Apr.  6,  1907,  1  p.  "Recent  Cyanide  Practice, "  p.  245. 

COLLINS,  E.  A.  All-sliming.  M.  &  S.  P.,  Sept.  18,  1909.  "More  Recent 
Cyanide  Practice, "  p.  300. 

CRANE,  W.  R.  Bibliography  of  fine  crushing  by  tube  and  other  mills, 
"Index  of  Mining  Engineering  Literature."  1909,  4  pp. 

DEL  MAR,  A.     Crushing  by  stages.     M.  &  S.  P.,  Nov.  5,  1910,  1  p. 

Efficiency  of  tube  mills.     Min.  World,  Feb.  12,  1910,  1  p. 

DENNY,  H.  S.  Fine-grinding.  •  Pac.  Miner,  Apr.,  1911,  1  p.;  Min.  Mag.. 
Mar.,  1911,  3  pp. 

Fine  grinding.     Min.  Mag.,  July,  1911. 

DOVETON,  G.  Fine-grinding.  M.  &  S.  P.,  Jan.  27,  1906,  1  p.  "Recent 
Cyanide  Practice, "  p.  16. 

DOWLING,  W.  R.  Tube-mill  practice.  Jour.  Ch.,  Met.,  &  Min.  Soc.,  S.  A., 
Apr.  to  Sept.,  1906,  16  pp. 

Critical  moisture  in  tube-mill  feed.     Min.  Mag.,  June,  1911. 

Stationary  amalgam  plates  in  tube-mill  plants.  Jour.  Ch.,  Met.,  &  Min. 
Soc.,  S.  A.,  Jan.,  1911,  1  p. 

DROTT,  M.     Tube  mills,  wet  and  dry.     Aust.  Min.  &  Eng.  Rev.,  Apr.  5, 

1909,  5  pp. 

DRUCKER,  A.  E.  Tube-milling  in  Korea.  M.  &  S.  P.,  Sept.  22,  1906,  1  p. 
"Recent  Cyanide  Practice,"  p.  110. 

Tube-mill  lining.  M.  &  S.  P.,  Nov.  17,  1906,  1  p.  "Recent  Cyanide 
Practice,"  p.  166. 

FISCHER,  H.  Operation  of  a  tube  mill.  Eng.  &  Min.  Jour.,  Nov.  17,  1904, 
2  pp.  " Notes  on  Metallurgical  Mill  Construction." 


254  TEXT  BOOK  OF  CYANIDE  PRACTICE 

FOOTE,  A.  D.  W.  Tube-mill  lining,  slime-filters,  and  patents.  M.  &  S.  P., 
Feb.  1,  1908,  1  p.  "  Recent  Cyanide  Practice,"  p.  111. 

Fox,  H.  W.  Economics  of  the  tube  mill.  Mines  and  Mins.,  June,  1908, 
4pp. 

Spiral  feeder  for  tube  mill.    Eng.  &  Min.  Jour.,  Dec.  14,  1907. 

GRAHAM,  K.  L.  Notes  on  some  recent  improvements  in  tube-mill  practice. 
Jour.  Ch.,  Met.,  &  Min.  Soc.,  S.  A.,  Apr.  to  Sept.,  1907,  13  pp. 

GROCH  (N.  C.)  and  NAGEL  (F.  J.).  Feeder  for  tube  mill.  M.  &  S.  P., 
Apr.  27,  1907,  1  p. 

HAMILTON,  E.  M.  All-sliming.  M.  &  S.  P.,  Aug.  21,  1909,  3  pp.  "  More 
Recent  Cyanide  Practice,"  p.  293. 

HARDINGE,  H.  W.  Conical  tube-mill.  M.  &  S.  P.,  Feb.  15,  1908,  2  pp. 
"More  Recent  Cyanide  Practice,"  p.  105. 

Crushing  by  stages.     M.  &  S.  P.,  Oct.  8,  1910,  1  p. 

Hardinge  conical  pebble-mill.     T.  A.  I.  M.  E.,  vol.  39,  1908,  5  pp. 

Hardinge  conical  tube-mill.     Eng.  &  Min.  Jour.,  Nov.  16,  1907,  1  p. 

Hardinge  conical  tube-mill.     West.  Ch.  &  Met.,  Apr.,  1908,  7  pp. 

Pebble-mill  amalgamation.     M.  &  S.  P.,  Apr.  30,  1910,  1  p. 

Problem  of  fine-grinding  in  tube  mills.  Eng.  &  Min.  Jour.,  Nov.  26,  1910, 
Ip. 

Tube-mill  lining.  M.  &  S.  P.,  Nov.  23,  1907,  and  Mar.  28,  1908,  2  pp. 
"More  Recent  Cyanide  Practice,"  p.  108. 

Tube  mills.  Eng.  &  Min.  Jour.,  June  8,  1905.  "Notes  on  Metallurgical 
Mill  Construction." 

Stage  crushing.     Eng.  &  Min.  Jour.,  Jan.  22,  1910,  1  p. 

HENDERSON,  E.  T.  Laboratory  screens.  Their  use  in  testing  efficiency 
of  grinding  machines.  Aust.  Min.  &  Eng.  Rev.,  Nov.  5,  1908,  3  pp. 

JAMES,  A.  Crushing  and  grinding  practice  at  Kalgoorlie.  M.  &  S.  P., 
July  28,  1906,  2  pp.  "Recent  Cyanide  Practice,"  p.  73. 

Tube-mill  notes.  Eng.  &  Min.  Jour.,  Mar.  16,  1905,  1  p.  "Notes  on 
Metallurgical  Mill  Construction."  Abstract  from  Inst.  Min.  &  Met.,  1905. 

KLUG,  G.  C.  Grinding  pan  practice.  Pipe  discharge  and  classification 
of  ground  product.  Jour.  W.  A.  Cham,  of  Mines,  Sept.  30,  1910,  4  pp. 

LAMB,  M.  R.  Crushing  at  cyanide  plants.  Eng.  &  Min.  Jour.,  Feb.  4, 
1911,  1  p. 

Crushing  machines  for  cyanide  plants.  T.  A.  I.  M.  E.,  vol.  41,  1910,  6  pp.; 
abstract  in  Min.  World,  July  30,  1910,  2  pp. 

Chile  mill.     Eng.  &  Min.  Jour.,  June  12,  1909,  1  p. 

LEUPOLD,  H.  Tube-mill  results.  Eng.  &  Min.  Jour.,  June  8,  1905;  ab- 
stract from  S.  A.  Assn.  of  Engrs. 

MACKAY,  A.  N.     Tube-mill  lining.     (Home  made.)     Min.  Mag.,  July,  1911. 

MEGRAW,  H.  A.  Some  characteristics  of  Chilean  mills.  Eng.  &  Min. 
Jour.,  Nov.  12,  1910,  2  pp. 

McMiKEN,  S.  D.  Tube-mill  lining.  M.  &  S.  P.,  Nov.  3,  1906,  1  p.  "Re- 
cent Cyanide  Practice,"  p.  162. 

Tube-mill  liners.     N.  Z.  Mines  Record,  Oct.  16,  1907. 

MITCHELL,  D.  P.  Pans  v.  tubes.  M.  &  S.  P.,  Aug.  4,  1906.  "Recent 
Cyanide  Practice,"  p.  78. 


CLASSIFIED  BIBLIOGRAPHY  255 

NEAL,  W.  Diaphragm  cones  and  tube-milling.  M.  &  S.  P.,  Apr.  2,  1910, 
2  pp.  "More  Recent  Cyanide  Practice,"  p.  389. 

RHODES,  C.  E.  Tube-mill  lining.  M.  &  S.  P.,  Dec.  21,  1907.  "More 
Recent  Cyanide  Practice, "  p.  109. 

RICHARDS,  R.  H.  Bibliography  for  pulverizers  other  than  gravity  stamps. 
Vol.  1,  "Ore  Dressing,"  1903,  p.  289. 

Bibliography  of  grinders  other  than  gravity  stamps.  Vol.  3,  "Ore  Dress- 
ing," 1909,  p.  1323. 

Complete  bibliography  for  pulverizers  other  than  gravity  stamps.  Vol.  4, 
"Ore  Dressing,"  1909,  p.  2013. 

ROBERTSON,  G.  A.  Distribution  of  pulp  in  tube-milling.  Min.  World, 
Oct.  29,  1910;  abstract  from  Jour.  Ch.,  Met.,  &  Min.  Soc.,  S.  A. 

Lay-out  of  a  tube-mill  plant.     S.  A.  Eng.  Jour.,  Mar.  18,  1911,  1  p. 

ROTHERHAM,  G.  H.  New  tube-mill  lining.  Min.  World,  Apr.  23,  1910, 
lp. 

SCHWERIN,  M.  Notes  on  some  regrinding  machines.  Eng.  &  Min.  Jour., 
Mar.  10,  1904,  3  pp.  "Notes  on  Metallurgical  Mill  Construction." 

SHAPELY,  C.  Method  of  returning  pulp  to  classifier  from  tube  mill.  Eng. 
&  Min.  Jour.,  Feb.  4,  1911. 

SHARPLEY,  H.     Feeder  for  tube  mill.     Eng.  &  Min.  Jour.,  July  8,  1911. 

SHERROD,  V.  B.  Grinding  tests  at  Pachuca,  Mex.  M.  &  S.  P.,  Mar.  5, 
1910,  3  pp.;  abstract  in  Trans.  Mex.  Inst. 

Pulp  classification  and  tube-mill  efficiency.  Met.  &  Chem.  Eng.,  Mar., 
1910,  5  pp. 

SIMPSON,  W.  E.  Grinding  machines  used  at  Kalgoorlie.  Eng.  &  Min. 
Jour.,  Nov.  14,  1903.  "Notes  on  Metallurgical  Mill  Construction." 

SMART,  G.  O.  Tube-mill  circuit  and  classification.  Jour.  Ch.,  Met.,  & 
Min.  Soc.,  S.  A.,  May,  1910,  4  pp.;  abstract  in  Min.  World,  May  7,  1910,  3  pp. 

STADLER,  H.  Efficiency  of  fine-grinding  machines.  Mines  &  Mins.,  June, 
1910,  2  pp.;  M.  &  S.  P.,  June  18,  1910,  1  p.;  abstract  from  Jour.  S.  A.  Assn. 
of  Engrs. 

STANLEY  (G.  H.)  and  WEBBER  (M.).  Laboratory  comparison  of  tube- 
mill  pebbles.  Jour.  Ch.,  Met.,  &  Min.  Soc.,  S.  A.,  June,  1908,  2  pp. 

STEWART,  J.  A.  Increased  milling  capacity  at  small  cost.  (Lane  slow- 
speed  mill.)  M.  &  S.  P.,  Feb.  2,  1907. 

TOD,  S.     Conical  tube-mill  grinding.     M.  &  S.  P.,  Aug.  20,  1910. 

URBITER,  W.  H.  Efficiency  of  fine-grinding  machinery.  Eng.  &  Min.  Jour., 
Aug.  5,  1911,  3  pp. 

VAN  LAW,  C.  W.  Tube  mills  at  Guanajuato.  M.  &  S.  P.,  Aug.  17,  1907. 
"Recent  Cyanide  Practice,"  p.  329. , 

VON  BERNEWITZ,  M.  W.  Concentration  of  slime.  (Tube-milling.)  M.  & 
S.  P.,  Dec.  10,  1910,  1  p. 

BaU  mill  practice  at  Kalgoorlie.     M.  &  S.  P.,  July  15,  1911,  2  pp. 

WAINWRIGHT  (W.  E.)  and  MCBRIDE  (W.  J.).  Tube-mill  and  grinding 
pans  at  Broken  Hills  South  mine.  (Comparative  test.)  Proc.  Aust.  Inst. 
Min.  Engrs.,  Feb.,  1909,  23  pp. 

WANN,  E.  E.  Fine-grinding.  M.  &  S.  P.,  Dec.  16  and  30,  1905;  Feb.  10, 
1906. 


256  TEXT  BOOK  OF  CYANIDE  PRACTICE 

WARWICK,  A.  W.  Influence  of  fine-grinding  on  metallurgy  of  precious 
metals.  West.  Ch.  &  Met.,  Mar.  and  Apr.,  1905,  48  pp. 

WEST,  H.  E.  Tube-mill  lining.  M.  &  S.  P.,  Mar.  28,  1908,  1  p.  "More 
Recent  Cyanide  Practice, "  p.  137. 

W^HITE,  H.  A.  Theory  of  tube  mill.  Jour.  Ch.,  Met.,  &  Min.  Soc.,  S.  A., 
May  to  Oct.,  1905;  abstract  in  Eng.  &  Min.  Jour.,  Sept.  23,  1905,  2  pp.; 
abstract  in  " Notes  on  Metallurgical  Mill  Construction." 

WHITMAN,  P.  R.  All-sliming.  M.  &  S.  P.,  Sept.  18,  1909.  "More  Recent 
Cyanide  Practice, "  p.  299. 

WILSON,  E.  B.     Tube-mill  crushing.     Mines  &  Mins.,  Aug.,  1908,  3  pp. 
YATES,  A.     Screen  analysis  and  grinding  efficiency.     M.  &  S.  P.,  May  1, 
1909,  1  p.;  abstract  from  Jour.  Ch.,  Met.,  &  Min.  Soc.,  S.  A. 
Engineering  and  Mining  Journal.     Abbe  tube-mill.     Dec.  20,  1904. 
El  Oro  tube-mill  lining.     Apr.  18,  1908. 
Lane  slow  speed  mill.     May  23,  1908,  1  p. 
Smooth  lining  for  tube  mills.     Apr.  30,  1910. 
Tube-mill  lining  in  use  on  the  Rand.     Aug.  6,  1910,  1  p. 
Giesecke  ball-tube  mill.     Eng.  &  Min.  Jour.,  Sept.  20,  1911;   Min.  &  Eng. 
World,  Aug.  5,  1911;  Mines  &  Mins.,  Sept.,  1911;  M.  &  S.  P.,  Sept.  30,  1911. 
Mines  and  Minerals.     Successful  tube-mill  lining.     Vol.  27,  p.  507,  1  p. 
Mining  Magazine.     Cobbe-Middleton  grinding  pan.     Nov.,  1909,  2  pp. 
Mining  and  Scientific  Press.      Regrinding.     Apr.  7,  1906,  1  p.     "Recent 
Cyanide  Practice,"  p.  29. 

Tube  mill.     Mar.  24,  1906. 
Tube-mill  liner.     Mar.  5,  1910. 

Tube-mill  lining.     July  28,  1906,  1  p.     "Recent  Cyanide  Practice," 
p.  69. 

Mining  World.     Tube-mill  practice  in  Mexico.     July  3,  1909. 
South  African   Mines.     Economics  of  tube-mills.     Oct.   27  to  Nov.   10, 
1906. 

South  African  Mining  Journal.     Stamps  and  tube-mills,  Apr.  30,  1910,  1  p. 
Tube-milling  practice.     Jan.  2,  1909,  2  pp. 
Review  of  present  day  tube-mill  practice  on  Rand.     Sept.  2,  1911. 

W.   Cyanidation  of  Silver  Ores,  and  in  Mexico 

BOYD,  T.  K.  Cyanidation  of  silver  ores.  Mex.  Min.  Jour.,  Oct.,  1909, 
2pp. 

Milling  practice  at  Altixtac,  Mex.,  Mex.  Min.  Jour.,  Sept.,  1911,  1  p. 

BRODIE,  W.  M.  Milling  of  Batopilas  native  silver  ore.  Mex.  Min.  Jour., 
Jan.,  1911,  3  pp.;  abstract  in  Pac.  Miner,  Jan.,  1911,  2  pp. 

BROWNE,  R.  S.     Cyaniding  silver  ores.     M.  &  S.  P.,  vol.  85,  p.  338,  1  p. 

BORDEAUX,,  A.  F.  J.  Cyaniding  of  silver  ores  in  Mexico.  T.  A.  I.  M.  E., 
vol.  40,  1909,  11  pp.;  vol.  41,  1910,  16  pp. 

BURGGROF,  J.  Loreto  cyanide  plant  of  Cia.  del  Real  Monte  y  Pachuca. 
Mex.  Min.  Jour.,  Aug.,  1910,  1  p. 

BURT,  E.  Milling  practice  at  El  Oro  mill,  Mex.  Min.  World,  Oct.  26, 
1907,  4  pp. 


CLASSIFIED   BIBLIOGRAPHY  257 

BURT  (E.)  and  CAETANI  (G.).  Fine-grinding  of  ore  by  tube  mills,  and 
cyaniding  at  El  Oro,  Mex.  T.  A.  I:  M.  E.,  vol.  37,  1906,  53  pp. 

BUTLER,  J.  S.  Milling  and  cyanide  practice,  San  Prospero  mill,  Guana- 
juato. M.  &  S.  P.,  July  25,  1908,  3  pp.  "More  Recent  Cyanide  Practice," 
p.  158. 

CHIDDY,  A.     Cyanidation  of  silver.     Eng.  &  Min.  Jour.,  June  1,  1905,  1  p. 

CLARK,  J.  E.     Cyaniding  base  silver  ores.     M.  &  S.  P.,  Aug.  7,  1911,  1  p. 

DAUE,  E.  O.  Notes  on  cyanide  practice  at  Pachuca.  Mex.  Min.  Jour., 
Oct.,  1908,  2  pp. 

DRISCOLL,  G.  E.  Cyaniding  silver  ores  in  Honduras.  Min.  Jour.,  Jan. 
29,  1910,  2  pp.;  M.  &  S.  P.,  Mar.  13,  1909,  2  pp.  "More  Recent  Cyanide 
Practice, "p.  253. 

EDMONSON,  H.  W.  Treatment  at  Rio  Plata  mining  company.  Mex.  Min. 
Jour.,  Aug.,  1910,  2  pp. 

ELWES,  H.  G.  Cyanidation  of  silver  in  Mexico.  Eng.  &  Min.  Jour.,  Mar. 
16,  1905,  2  pp. 

EMPSON,  J.  B.  Silver  cyaniding  in  Mexico.  Eng.  &  Min.  Jour.,  Oct.  3, 
1908,  1  p. 

FERRIS,  W.  S.  Moore  filter  at  San  Rafael.  Mex.  Min.  Jour.,  Aug.,  1910, 
3pp. 

FIELD,  H.  C.  Practice  at  Pinguico  mill,  Guanajuato.  Mex.  Min.  Jour., 
July,  1911,  1  p. 

FLYNT,  A.  Cyanide  practice  at  Compania  Minera  de  los  Reyes.  Mex. 
Min.  Jour.,  Aug.,  1910,  4  pp. 

FULTON,  C.  A.  Cyanide  practice  at  Guanajuato.  Mex.  Min.  Jour.,  Aug., 
1910,  9  pp. 

GIRAULT,  E.  San  Rafael  cyanide  mill,  Pachuca.  Trans.  Mex.  Inst., 
Dec.,  1909,  21  pp.;  abstract  in  Eng.  &  Min.  Jour.,  July  9  and  Oct.  1,  1910, 
5  pp.;  abstract  in  Met.  &  Chem.  Engr.,  Mar.,  1910,  5  pp. 

Methods,  results,  and  costs  at  San  Rafael  y  Anexas  Co.,  Pachuca.  Mex. 
Min.  Jour.,  June,  1911,  2  pp. 

GONZALES  (F.),  GROTHE  (A.),  and  SALAZARS  (L.).  San  Rafael  mill  at 
Pachuca,  Mex.  Min.  &  Eng.  World,  Aug.  26,  1911,  2  pp. 

GRIFFITHS  (A.  P.)  and  OLDFIELD  (F.  W.).  Cyaniding  some  silver  ores  by 
percolation.  Inst.  Min.  &  Met.,  vol.  12,  1903,  10  pp.;  abstract  in  Eng.  & 
Min.  Jour.,  July  18,  1903,  1  p. 

HOBSON,  F.  J.  Cyanide  process  at  Guanajuato.  M.  &  S.  P.,  Jan.  6,  1906, 
1  p.  " Recent  Cyanide  Practice,"  p.  12. 

Peregrina  mill,  Guanajuato.     Eng.  &  Min.  Jour.,  May  19,  1906,  2  pp. 

HOYLE,  C.  New  Esperanza  mill  and  milling  practice.  Mex.  Min.  Jour., 
Aug.,  1910,  5  pp. 

JANIN,  L.  Cyanide  of  potassium  as  a  lixiviation  agent  for  silver  ores  and 
minerals.  Eng.  &  Min.  Jour.,  Dec.  29,  1888. 

KLINE,  R.  C.  Treatment  of  silver  ores  at  Guanaceva,  Mexico.  M.  &  S.  P., 
Mar.  18,  1911,  2  pp. 

KNIFFEN,  L.  B.  Cyanidation  of  silver  ores.  M.  &  S.  P.,  Feb.  2&,  1910, 
1  p.  "More  Recent  Cyanide  Practice,"  p.  382. 

Cyanide  experiences  in  Northern  Mexico,    Mex,  Min.  Jour,,  Aug.,  1910, 


258          TEXT  BOOK  OF  CYANIDE  PRACTICE 

3  pp.;  abstract  in  Pac.  Miner,  Sept.,  1910;  abstract  in  Jour.  Ch.,  Met.,  & 
Min.  Soc.,  S.  A.,  Mar.,  1911. 

Deadwood  mill  at  Mongollon,  N.  Mex.  (Silver  sulphide  ore.)  Eng.  & 
Min.  Jour.,  Oct.  14,  1911,  1  p. 

LAMB,  M.  R.  Cyanide  operations  in  Mexico  during  1908.  Min.  World, 
Feb.  6,  1909,  4  pp. 

Metallurgy  in  Western  Chihuahua.     Mex.  Min.  Jour.,  Nov.,  1908,  1  p. 

Milling  and  cyaniding  methods  in  Mexican  camps.  Min.  World,  Apr.  11, 
1908,  3  pp. 

Minas  Prietas  Reduction  Works.     M.  &  S.  P.,  Aug.  4,  1906,  2  pp. 

Present  cyanide  practice  in  Mexico.     Eng.  &  Min.  Jour.,  Apr.  4,  1908,  7  pp. 

Table  of  practice  in  Mexican  cyanide  mills.  Eng.  &  Min.  Jour.,  Apr.  3, 
1909. 

LINTON,  R.  Silver  ore  treatment  in  Mexico.  (Referring  to  manganese 
ore.)  Jour.  Ch.,  Met.,  &  Min.  Soc.,  S.  A.,  Aug.,  1908,  and  Mar.,  1909. 

MACDONALD,  B.  Cyanidation  of  silver  ores  at  Guanajuato.  Eng.  &  Min. 
Jour.,  Apr.  4,  1908,  8  pp. 

Development  of  cyanide  process  for  silver  ores  in  Mexico.  Eng.  &  Min. 
Jour.,  Apr.  18,  1908,  2  pp. 

Inauguration  of  cyanide  era  in  Parral  district.  Mex.  Min.  Jour.,  Aug., 
1910,  5  pp. 

MEGRAW,  H.  A.  Reconstruction  of  Angustias  cyanide  mill.  Eng.  &  Min. 
Jour.,  Aug.  13,  1910,  2  pp. 

MENNELL,  J.  L.  Recent  advance  in  cyanidation  in  Mexico.  Min.  World, 
Oct.  26,  1907,  2  pp. 

NARVAEZ,  F.  Metallurgical  practice  at  Hacienda  de  la  Union.  Eng.  & 
Min.  Jour.,  Nov.  21,  1908,  3  pp. 

NICOL,  J.  M.  Metallurgical  methods  at  Pachuca.  Min.  Mag.,  Feb., 
1910,  9  pp. 

OXNAM,  T.  H.  Cyaniding  silver-gold  ores  of  Palmarejo  mine,  Chihuahua, 
Mex.  T.  A.  I.  M.  E.,  vol.  36,  1905,  54  pp.;  abstracts  in  Eng.  &  Min.  Jour., 
Aug.  19  to  Sept.  9,  1905,  11  pp.;  in  M.  &  S.  P.,  July  29  to  Sept.  9,  1905,  10  pp.; 
in  Hoffman's  " Hydrometallurgy  of  Silver,"  42  pp. 

PAUL,  W.  H.  Cyanide  practice  at  Dolores  mine  in  Mexico.  Bull.  Colo. 
Sch.  of  Mines,  May,  1910,  4  pp. 

QUARTANO,  A.  Cyanide  year  at  Dos  Estrellas.  Mex.  Min.  Jour.,  Aug., 
1910,  1  p. 

REID,  J.  A.  Cyanidation  of  silver-gold  ores  at  Guanajuato.  Min.  World, 
Apr.  9,  1910,  -2  pp. 

RICE,  C.  T.  Cyanidation  of  silver  ores,  Pachuca.  Eng.  &  Min.  Jour., 
Oct.  3,  1908,  7  pp. 

Cyanide  mills  of  Guanajuato  Development  Co.  Eng.  &  Min.  Jour.,  Nov. 
14  and  21,  1908,  9  pp. 

El  Rayo  gold  mine  and  mill,  near  Santa  Barbara,  Mex.  Eng.  &  Min.  Jour., 
July  11,  1908,  3  pp. 

Jesus  Maria  and  Flores  mills,  Guanajuato.  Eng.  &  Min.  Jour.,  Sept.  26, 
1908,  5  pp. 

Milling  and  cyanide  practice  at  El  Oro.   Eng.  &  Min.  Jour.;  Apr.  3, 1909, 8  pp. 


CLASSIFIED  BIBLIOGRAPHY  259 

New  Esperanza  mill  at  El  Oro.     Eng.  &  Min.  Jour.,  Oct.  17,  1908,  3  pp. 
Some  metallurgical  processes  at  Pachuca,  Mexico.     Eng.  &  Min.  Jour., 
Sept.  19,  1908,  4  pp. 

Veta  Colorado  cyanide  mill,  Parral,  Mex.     Eng.  &  Min.  Jour.,  July  18, 

1908,  3  pp. 

RICKARD,  T.  A.  Cyanide  practice  at  El  Oro.  M.  &  S.  P.,  Sept.  29  and 
Oct.  6,  1906,  7  pp.  "Recent  Cyanide  Practice, "  pp.  114  and  125. 

Old  and  new  methods  at  Guanajuato.  M.  &  S.  P.,  June  29,  1907,  2  pp. 
"Recent  Cyanide  Practice,"  p.  296. 

Metallurgical  development  at  Guanajuato.  M.  &  S.  P.,  May  18,  1907, 
2  pp.  "Recent  Cyanide  Practice, "  p.  254. 

SCOBEY,  J.  Ore  treatment  at  Virginia  and  Mexico  mill,  Jalisco.  Eng.  & 
Min.  Jour.,  Oct.  2,  1909,  1  p. 

SEAMON,  W.  H.  Yoquivo  mine  and  mill,  Western  Chihuahua.  Eng.  & 
Min.  Jour.,  Oct.  22,  1910,  2  pp. 

SHAPELY,  C.  Slime  treatment  at  Santa  Natalia  mill.  Eng.  &  Min.  Jour., 
Aug.  20,  1910,  1  p. 

SHAPELY,  E.  All-slime  cyanide  plant  at  Guanajuato,  Mex.  Eng.  &  Min. 
Jour.,  July  10,  1909. 

SHERROD,  V.  B.  Some  features  in  work  of  Guerrero  mill,  Pachuca.  Trans. 
Mex.  Inst.,  Dec.,  1909,  4  pp. 

Some  notes  on  combination  processes  for  treatment  of  silver  ores.  Mex. 
Min.  Jour.,  Apr.,  1911,  1  p. 

SWEETLAND,  E.  J.  Treatment  of  silver-lead  tailing  by  cyanide  process. 
Eng.  &  Min.  Jour.,  Aug.  25,  1906,  2  pp. 

THOMAS,  K.  Guerro  mill  at  Real  del  Monte,  Hidalgo.  Mex.  Min.  Jour., 
Jan.  9,  1909,  2  pp. 

TWEEDY  (G.  A.)  and  BEALS  (R.  L.).  Cyanide  plant  and  practice  at  Minas 
del  Tajo,  Sinaloa,  Mex.  T.  A.  I.  M.  E.,  vol.  41,  1910,  44  pp.;  abstract  in 
Eng.  &  Min.  Jour.,  Mar.  12,  1910,  4  pp.;  abstract  in  Min.  World,  Mar.  12, 
and  19,  1910,  9  pp. 

VAN  LAW,  CARLOS  W.  Cyanide  plant  for  treating  Guanajuato  ores. 
Eng.  &  Min.  Jour.,  Apr.  6,  1907,  3  pp. 

VAN  SUAN,  P.  E.  Cyaniding  at  Guazapaies,  Mex.  Eng.  &  Min.  Jour., 
Oct.  7,  1911,  2  pp. 

WESTON,  W.  Santa  Gertrudis  cyanide  mill.  Eng.  &  Min.  Jour.,  July  15, 
1911,  2  pp. 

WILLIS,  H.  T.     Cyanidation  of  Parral  silver  ores.     M.  &  S.  P.,  Apr.  3, 

1909,  2  pp.     Mex.  Min.  Jour.,  May,  1909,  2  pp. 

Engineering  and  Mining  Journal.  Cyanide  practice  at  El  Tajo  mine, 
Jalisco,  Mex.  Jan.  29,  1910,  1  p. 

Mining  and  Scientific  Press.  Dos  Estrellas  mill.  (Costs  and  method.) 
Feb.  8,  1908,  2  pp.  "More  Recent  Cyanide  Practice,"  p.  118. 

Metallurgical  chart  of  operations  in  Butters  Copala  mill,  Mex.      (No 
text.)     Feb.  16,  1907,  1  p. 

Recent  cyanide  mill  of  Guanajuato  R.  and  M.  Co.     May  23,  1908,  1  p. 
"More  Recent  Cyanide  Practice,"  p.  143. 
Mining  World.     Mining  and  milling  at  Guanajuato.     Oct.  26,  1907,  5  pp. 


260          TEXT  BOOK  OF  CYANIDE  PRACTICE 

X.   Cyanidation  in  United  States  and  Canada 

1.  NEVADA 

ADAMS,  W.  S.     Cyanide  practice  at  the  Darby,  Nevada,  Ore  Reduction 
Co.     Mex.  Min.  Jour.,  Aug.,  1910,  1  p. 

AYRES,  E.  R.     Bullfrog  cyanide  mill.     Eng.  &  Min.  Jour.,  Feb.  23,  1907. 

BARBOUR,  P.  E.     Goldfield  Consolidated  600-ton  mill.     Eng.  &  Min.  Jour., 
Sept.  5,  1908,  8pp. 

BOSQUI,   F.  L.     Milling  v.  smelting  in  treatment  of  Tonopah-Goldfield 
ores.     M.  &  S.  P.,  Mar.  31,  1906,  1  p.     "Recent  Cyanide  Practice,"  p.  33. 

Ore  treatment  at  Combination  mine,  Goldfield.     M.  &  S.  P.,  Oct.  6  and  13, 
1906,  6  pp.     "Recent  Cyanide  Practice,"  p.  136. 

Treatment  of  Desert   ores.     M.  &  S.   P.,  May  26,  1906,  1  p.     "Recent 
Cyanide  Practice,"  p.  51. 

BROWNE,  R.  S.     Cyanidation  in  Nevada.     M.  &  S.  P.,  Nov.  30,   1907. 
"More  Recent  Cyanide  Practice,"  p.  39. 

CAMPBELL,  B.  P.     Windfall  mine  and  mill.     Pac.  Miner,  Sept.,  1909,  2  pp. 

COLLINS,  E.  A.     Cyanidation  in  Nevada.     M.  &  S.  P.,  Jan.   11,   1908= 
"More  Recent  Cyanide  Practice,"  p.  40. 

CREHORE,  L.  W.     Modern  cyanide  mill  at  Mazuma,  Nev.     Min.  World, 
Sept.  11,  1909,  1  p. 

GAYFORD,  E.     Details  of  cyaniding  at  Fay,  Nevada.     M.  &  S.  P.,  Oct.  25, 
1902,  1  p. 

HANSON,  H.     Mines  and  plants  of  Pittsburgh-Silver  Peak.     M.  &  S.  P., 
May  8,  1909,  5  pp.     "More  Recent  Cyanide  Practice,"  p.  263. 

Pittsburgh-Silver  Peak  mill.     Mines  &  Mins.,  July,  1909,  4  pp. 

HUNT,  B.     Cyanidation  in  Nevada.     M.  &  S.  P.,  Feb.  22,  1908,  1  p.     "  More 
Recent  Cyanide  Practice,"  p.  48. 

Treatment  of  Desert  ores.     M.  &  S.  P.,  Apr.  28  and  June  23,  1906.     "Re- 
cent Cyanide  Practice,"  pp.  65  and  247. 

HUTCHINSON,  J.  W.     Operations  of  Goldfield  Consolidated  Mill,  Nevada. 
M.  &  S.  P.,  May  6  to  June  10,  1911.     Reprinted  in  pamphlet  form. 

KING,  L.  M.     Cyanidation  in  Nevada.     M.  &  S.  P.,  Jan.  25,  1908,  3  pp. 
"More  Recent  Cyanide  Practice,"  p.  41. 

Treatment  of  Desert  ores.     M.  &  S.  P.,  Aug.   25,  1906,  1  p.     "Recent 
Cyanide  Practice, "  p.  82. 

KIRBY,  A.  G.     Cyanidation  in  Nevada.     M.  &  S.  P.,  June  20,  1908,  4  pp. 
"More  Recent  Cyanide  Practice,"  p.  50. 

KIRCHEN,  J.  C.     Tonopah-Extension  mill.      M.  &  S.  P.,  Apr.  9,  1910,  2  pp. 

LAMB,  M.  R.     Stamp-mill  and  cyanide  plant  of  Combination  Mines  Co. 
Eng.  &  Min.  Jour.,  June  30,  1906,  2  pp. 

LEAVER,  E.  S.     Milling  practice  in  Nevada-Goldfield  Reduction  Works. 
M.  &  S.  P.,  Aug.  22,  1908,  1  p.     "More  Recent  Cyanide  Practice, "  p.  198. 

MAGENAU,  W.     Cyaniding  stamp-mill  tailing  at  Tuscarora,  Nev.     Mines 
&  Mins.,  vol.  21,  p.  299,  2  pp. 

MARTIN,  A.  H.     Goldfield  Consolidated  mill.     Min.  Sci.,  Feb.  11,  1909, 
2pp. 


CLASSIFIED   BIBLIOGRAPHY  261 

Hundred-stamp  Deseret  mill  at  Millers,  Nev.  Min.  World,  May  1,  1909, 
3pp. 

Milling  conditions  in  Goldfield  district,  Nev.     Min.  World,  Mar.  13,  1909, 

5  pp. 

Milling  methods  at  Grass  Valley  and  Nevada  City.  Pac.  Miner,  Aug., 
1909,  3  pp.;  Min.  World,  Dec.  4,  1909,  3  pp. 

Mill  of  Tonopah  Mining  Co.     Min.  Sci.,  Feb.  24,  1910,  2  pp. 

Montana-Tonopah  mine  and  mill.     Min.  World,  Mar.  12,  1910,  2  pp. 

Montgomery-Shoshone  mill.     M.  &  S.  P.,  Feb.  19,  1910,  2  pp. 

Pittsburgh-Silver  Peak  mill.     Min.  World,  Sept.  10,  1910,  2  pp. 

Silver  Peak  mill.     Min.  Sci.,  Nov.  18,  1909,  1  p. 

Tonopah  Extension  mine  and  mill.     Pac.  Miner,  Oct.,  1910,  2  pp. 

Treating  low  grade  ore  at  Comstock  lode.  (Butters  plant.)  Min.  Sci., 
Jan.  21,  1909,  2  pp. 

MORRIS,  H.  G.     Equipment  and  practice  at  Florence-Goldfield  mill.     Eng. 

6  Min.  Jour.,  Feb.  12,  1910,  3  pp. 

PARSONS,  A.  R.  Deseret  mill,  Millers,  Nev.  M.  &  S.  P.,  Oct.  19,  1907, 
4  pp.  "More  Recent  Cyanide  Practice,"  p.  9. 

Nevada  cyanide  practice.     Mex.  Min.  Jour.,  Aug.,  1911,  1  p. 

RICE,  C.  T.  Butters  cyanide  plant,  Virginia  City,  Nev.  Eng.  &  Min. 
Jour.,  Feb.  9,  1907,  5  pp. 

Milling  at  the  Florence-Goldfield.     Eng.  &  Min.  Jour.,  Apr.  15,  1911,  2  pp. 

Tonopah-Belmont  cyanide  plant.     Eng.  &  Min.  Jour.,  July  15,  1911,  4  pp. 

Tonopah-Belmont  surface  plant.     Eng.  &  Min.  Jour.,  Apr.  29,  1911,  3  pp. 

RICKARD,  T.  A.     Metallurgical  development  at  Goldfield,  Nevada.     M.  & 

5.  P.,  June  20,  1908,  3  pp.     "More  Recent  Cyanide  Practice,"  p.  151. 
ROTHERHAM,    G.    H.     Milling   plant   of   Montana-Tonopah    Mining   Co. 

M.  &  S.  P.,  Sept.  5,  1908,  4  pp.     "More  Recent  Cyanide  Practice,"  p.  201. 
TYSSOWSKI,   J.     Goldfield   Consolidated   mill  operations.     Eng.   &   Min. 
Jour.,  June  11,  1910,  1  p. 

VAN  SAUN,  P.  E.  Cyaniding  at  Montgomery-Shoshone  mill.  Eng.  & 
Min.  Jour.,  Jan.  22,  1910,  3  pp.  Mines  &  Mins.,  Mar.,  1908,  2  pp. 

Nevada  Wonder  Co.'s  new  mill.    Min.  &  Eng.  World,  Nov.  11,  1911,  4  pp. 
WOLCOTT,  G.  E.     Mines  and  mills  of  Tonopah,  Nev.     Eng.  &  Min.  Jour., 
Mar.  20,  1909,  3  pp. 

Engineering  and  Mining  Journal.  New  mill  of  Tonopah  Extension  Min- 
ing Co.  May  21,  1910,  1  p. 

Montana-Tonopah  stamp  and  cyanide  mill.     May  9,  1908,  3  pp. 
Wet-crushing    cyanide   plant    at    Ely,    Nevada.     (Chainman   mine.) 
Dec.  7,  1901,  2  pp. 
Mining  Science.     Goldfield  Consolidated  mill.     May  7,  1908,  1  p. 

2.    BLACK  HILLS 

BOSQUI,  F.  L.     Cyanide  practice  at  Homestake  Mills.     M.  &  S.  P.,  July 

6,  1907,  3  pp.     "Recent  Cyanide  Practice,"  p.  302. 

CLARK  (A.  J.)  and  SHARWOOD  (W.  J.).  Notes  on  cyaniding  methods  at 
Homestake.  Min.  World,  Mar.  26,  1910,  2  pp.;  abstract  from  Jour.  Ch., 
Met.,  &  Min.  Soc.,  S.  A. 


262  TEXT  BOOK  OF  CYANIDE  PRACTICE 

FULTON,  C.  H.  Crushing  in  cyanide  solution  as  practiced  in  Black  Hills. 
T.  A.  I.  M.  E.,  vol.  35,  1904,  28  pp.;  M.  &  S.  P.,  vol.  89,  pp.  207,  224,  243,  260, 
273,  290,  and  310,  7  pp. 

Cyanide  process  in  Black  Hills.  Bull.  No.  5  of  South  Dakota  Sch.  of  Mines, 
Feb.,  1902,  87  pp. 

Metallurgical  practice  in  Black  Hills.  Bull.  No.  7  of  South  Dakota  Sch. 
of  Mines,  June,  1904,  63  pp. 

Metallurgical  practice  in  Black  Hills.     Mines  &  Mins.,  Apr.,  1905,  3  pp. 

GROSS,  J.  Cyanide  practice  at  the  Maitland  properties.  T.  A.  I.  M.  E., 
vol.  35,  1904,  20  pp.;  abstract  in  Eng.  &  Min.  Jour.,  Oct.  20,  1904,  1  p.;  abstract 
in  M.  &  S.  P.,  Dec.  10  to  31,  1904. 

HENTON,  J.  H.  Wet-crushing  and  cyaniding  siliceous  ores  of  Black  Hills. 
M.  &  S.  P.,  vol.  80,  p.  261. 

Some  further  mill  practice  in  cyaniding  siliceous  ores  of  Black  Hills.  M. 
&  S.  P.,  vol.  81,  p.  284  (Sept.  8,  1900),  1  p. 

MAGENAU,  W.  Present  practice  of  cyanidation  in  Black  Hills.  Eng.  & 
Min.  Jour.,  Aug.  11  and  18,  1904,  6  pp. 

MERRILL,  C.  W.  Metallurgy  of  Homestake  ores.  T.  A.  I.  M.  E.,  vol.  34, 
1903,  14  pp.;  abstracts  in  M.  &  S.  P.,  Oct.  3  to  24,  1903,  3  pp.;  Eng.  &  Min. 
Jour.,  Mar.  7,  1903,  2  pp.;  Mines  &  Mins.,  Dec.,  1903,  1  p.;  M.  &  S.  P.,  Mar. 
7,  1903,  1  p. 

MILLIKEN,  J.  T.  Cyaniding  in  Black  Hills.  M.  &  S.  P.,  vol.  89,  p.  176, 
lp. 

O'BRIEN,  B.  D.  Cyaniding  Black  Hills  "blue  ores."  Mines  &  Mins., 
Apr.,  1909,  5  pp. 

SAWYER,  E.  B.  Direct  wet-crushing  cyanide  mill  of  Black  Hills.  M.  <fe 
S.  P.,  vol.  83,  p.  202,  1  p. 

Cyanide  mill  of  Black  Hills.     M.  &  S.  P.,  vol.  83,  p.  246. 

SIMMONS,  J.  Wasp  No.  2  cyanide  mill,  Black  Hills.  Min.  World,  Dec. 
24,  1910,  2  pp. 

Trojan  cyanide  mill,  Black  Hills.     Eng.  &  Min.  Jour.,  Aug.  19,  1911,  2  pp. 

Mining  and  Scientific  Press.     Cyanide  plant  of  Dakota  Mining  and  Milling 
Co.     Apr.  19,  1902,  1  p.;  abstract  Bull.  No.  5  of  South  Dakota  Sch.  of  Mines. 
Cyanide  plant  of  Wasp  No.  2  Mining  Co.     Apr.  26,  1902,  1  p. 
Golden  Gate  cyanide  plant,  Black  Hills.     May  17  and  24,  1902,  3  pp.; 
abstract  Bull.  No.  5  of  South  Dakota  Sch.  of  Mines. 
Homestake  cyanide  plant.     Vol.  89,  p.  339,  1  p. 

Metallurgy  of  Homestake  ore.     (Costs  of  clean-up,  etc.)     Feb.  20, 
1904;  abstract  from  T.  A.  I.  M.  E. 

Portland  cyanide  mill.     May  10,  1902,  1  p.;  abstract  from  Bull.  No.  5 
of  South  Dakota  Sch.  of  Mines. 

3.    OUTSIDE  OF  NEVADA  AND  BLACK  HILLS 

AIKINS,  C.  T.  Cyanide  plant  of  Rose  Gold  Mining  Co.,  Victor,  Calif. 
Eng.  &  Min.  Jour.,  vol.  69,  p.  46,  1  p. 

ALDERSON,  M.  W.  Cyaniding  at  Gilt  Edge,  Montana.  M.  &  S.  P.,  Oct. 
7,  1899,  1  p. 


CLASSIFIED   BIBLIOGRAPHY  263 

Cyanide  process  in  Montana.  Eng.  &  Min.  Jour.,  vol.  75,  p.  221,  1  p. 
Mines  &  Mins.,  July,  1903. 

ALLEN,  R.  H.  Mines  and  mills  of  Consolidated  Mercur  Co.,  Utah.  Eng. 
&  Min.  Jour.,  June  18,  1910,  5  pp. 

BELL,  J.  R.  Cyaniding  in  telluride  district.  (Liberty  Bell  mill.)  Mines 
&  Mins.,  Apr.,  1902,  2-pp. 

CASE,  H.  R.  Cyaniding  tailing  in  Sierra  Co.,  Calif.  M.  &  S.  P.,  May  16, 
1903. 

CHASE,  C.  A.  Liberty  Bell  mill.  Trans.  A.I.M.E.,  Oct.,  1911;  abstract  in 
M.  &  S.  P.,  June  24,  1911,  2  pp. 

CHAUVENET,  R.  Cyanide  process  at  Portland  Mill,  Colorado.  Min. 
Reptr.,  Oct.  24  and  31,  1907,  5  pp. 

CHRISTENSEN,  C.  A  100-ton  modern  cyanide  plant.  Min.  World,  Nov. 
13,  1909,  3  pp. 

CLARK,  V.  V.  Cyanide  process  in  New  Mexico.  Bull.  Univ.  of  New  Mex., 
1900,  8  pp. 

COLLIE,  J.  E.  Ore  treatment  at  Mono  mine,  Siskiyou  Co.,  Calif.  Pac. 
Miner,  Dec.,  1909,  2  pp. 

DARTMOUTH,  H.  W.  Description  of  Empire  cyanide  plant,  Grass  Valley, 
Calif.  Pac.  Miner,  Apr.,  1911,  2  pp. 

DEL  MAR,  A.  Cyaniding  the  ores  of  Eastern  Oregon.  Eng.  &  Min.  Jour., 
Mar.  26,  1910,  1  p. 

EDGERTON,  W.     New  Portland  mill.     Min.  Sci.,  July  28,  1910,  3  pp. 

GAYFORD,  E.  Cyaniding  in  southern  (U.  S.)  states.  M.  &  S.  P.,  Feb.  27, 
1904,  1  p. 

GOODALE,  S.  L.  Milling  practice  at  Camp  Bird.  Eng.  &  Min.  Jour., 
May  4,  1905,  2  pp. 

GROPELLO,  E.  F.     Method  of  working  Taylor  mine  cyanide  plant,  Calif. 
M.  &  S.  P.,  Oct.  28,  1899,  1  p. 

HOLDEN,  E.  C.  Cyanide  plant  and  practice  at  Ymir  mine,  B.  C.  T.  A.  I. 
M.  E.,  vol.  34,  1903,  9  pp.;  abstracts  in  Eng.  &  Min.  Jour.,  Nov.  14,  Dec.  5 
and  17,  1903,  3  pp.;  Mines  &  Mins.,  Jan.,  1904;  M.  &  S.  P.,  Oct.  17  and 
24,  1903,  2  pp. 

LAY,  D.  Cyanide  practice  at  Reliance  mill,  B.  C.  Eng.  &  Min.  Jour., 
Apr.  20,  1907,  2  pp. 

LEONARD,  F.  Cyanide  practice  on  Boulder  Co.  ores.  West.  Ch.  &  Met., 
Jan.,  1907,  5  pp. 

MAGENAU,  W.  Some  observations  on  practice  of  cyanide  process  at  Mercur, 
Utah.  M.  &  S.  P.,  Apr.  21  to  May  5,  1900,  3  pp. 

MARTEL,  J.  L.  Mining  and  milling  practice  at  Queen  Esther  mine,  Calif. 
Min.  Sci.,  Dec.  19,  1907,  2  pp. 

MEGRAW,  H.  A.  Cyanidation  in  the  South.  (North  Carolina.)  Eng.  & 
Min.  Jour.,  Apr.  13,  1905,  1  p. 

MERRILL,  C.  W.  Application  of  cyanide  process  at  Mercur  mine.  Eng. 
&  Min.  Jour.,  vol.  54,  p.  440,  1  p. 

PACKARD,  G.  A.  Cyanide  process  in  U.  S.  T.  A.  I.  M.  E.,  vol.  26,  1896, 
12pp. 

PALMER,  L.  A.  Cyanidation  at  Mercur,  Utah.  M.  &  S.  P.,  May  1,  1909, 
3  pp.  "More  Recent  Cyanide  Practice,"  p.  256. 


264  TEXT  BOOK  OF  CYANIDE  PRACTICE 

PURRINGTON,  WOODS,  and  DOVETON.  Camp  Bird  mine  and  mill.  T.  A. 
I.  M.  E.,  vol.  33,  1902,  51  pp.;  abstract  in  M.  &  S.  P.,  Apr.  11  to  May  2,  1903, 
4pp. 

SHAW,  S.  F.  Cyanide  practice  in  U.  S.  and  Mexico.  Min.  World,  Aug.  7 
and  14,  1909,  4  pp.;  abstract  from  T.  A.  I.  M.  E. 

Standard  Consolidated  cyanide  mill,  Bodie,  Calif.  Eng.  &  Min.  Jour., 
Mar.  6,  1909,  2  pp. 

TRACY,  W.  E.  Cyanide  practice  at  Liberty  Bell  mill,  Colo.  Eng.  &  Min. 
Jour.,  vol.  82,  p.  149. 

TYSSOWSKI,  J.  F.  Hydrometallurgical  operations  at  Cobalt.  Eng.  & 
Min.  Jour.,  Dec.  24,  1910,  6  pp. 

Cyaniding  at  North  Star  mine  in  California.  Eng.  &  Min.  Jour.,  Aug.  27, 
1910,  3  pp. 

WOLCOTT,  G.  E.  Milling  at  Grass  Valley  and  Nevada  City,  Calif.  Eng. 
&  Min.  Jour.,  Feb.  27,  1909,  3  pp. 

WOODS,  G.  W.  Boston-Sunshine  mill,  Utah.  M.  &  S.  P.,  Aug.  28,  1909, 
1  p.  "More  Recent  Cyanide  Practice,"  p.  303. 

Y.   Cyanidation  in  South  Africa 

AARON,  C.  H.  Cyanide  process  in  South  Africa.  M.  &  S.  P.,  Nov.  19, 
1892,  1  p. 

CARTER,  T.  L.     Metallurgy  of  the  Rand.     Min.  Mag.,  Sept.,  1909,  3  pp. 

CHESTER,  E.  P.  Treatment  of  tailing  in  the  Witwatersrand.  Eng.  & 
Min.  Jour.,  vol.  66,  p.  5,  1  p. 

COOK,  R.  C.  H.  Ore  treatment  at  Giant  mine  in  Rhodesia.  Min.  World, 
Apr.  10,  1909,  2  pp.;  abstract  from  Jour.  Ch.,  Met.,  &  Min.  Soc.,  S.  A. 

DENNY,  G.  A.  So-called  " Denny"  metallurgy  on  Rand.  Mex.  Min. 
Jour.,  Aug.,  1910,  12  pp. 

DENNY,  H.  S.  Observations  on  metallurgical  practice  of  Witwatersrand. 
Jour.  Ch.,  Met.,  &  Min.  Soc.,  S.  A.,  July,  1903,  35  pp.;  Nov.,  1903,  11  pp.; 
Dec.,  1903,  2  pp.;  Jan.,  1904,  7  pp.;  Apr.,  1904,  11  pp.;  abstracts  in  M.  & 
S.  P.,  Feb.  13  and  June  25,  1904,  2  pp. 

DENNY,  G.  H.  and  H.  S.  Metallurgical  development  on  the  Rand.  M.  & 
S.  P.,  June  2,  1906,  1  p.  "Recent  Cyanide  Practice,"  p.  59. 

Recent  innovations  in  Rand  metallurgical  practice.  Eng.  &  Min.  Jour., 
Dec.  29,  1906,  6  pp. 

DURANT,  H.  T.  Notes  on  limitations  of  cyanide  process.  Jour.  Ch., 
Met.,  &  Min.  Soc.,  S.  A.,  Dec.,  1903,  and  Feb.,  1904,  3  pp. 

EISSLER,  M.  Practical  operations  of  cyanide  process  on  Transvaal  gold 
fields.  Inst.  Min.  &  Met.,  vol.  3,  1894,  64  pp. 

FELDTMAN,  W.  F.  Cyanide  process  in  Transvaal.  Eng.  &  Min.  Jour., 
Aug.  4  and  11,  1894,  4  pp. 

HATCH,  F.  H.  Evolution  of  Rand  cyanide  practice.  Eng.  &  Min.  Jour., 
July  22,  1911,  1  p.:  Min.  &  Eng.  World,  July  29,  1911,  3  pp. 

JAMES,  A.  Metallurgical  progress  in  South  Africa  and  Australia.  Eng. 
&  Min.  Jour.,  Jan.  5,  1905,  2  pp. 

THOMAS,  J.  E.     Operation  of  small  cyanide  plants  in  Rhodesia.     Jour. 


CLASSIFIED   BIBLIOGRAPHY  265 

Ch.,  Met.,  &  Min.  Soc.,  S.  A.,  Sept.,  1909,  4  pp.;  abstract  in  Min.  World, 
Dec.  25,  1909,  2  pp. 

Simmer  Deep  and  Jupiter  reduction  works.  M.  &  S.  P.,  Sept.  18,  1909, 
2  pp.  "More  Recent  Cyanide  Practice,"  p.  305. 

WESTON,  E.  M.  Analysis  of  mine  and  mill  practice  on  the  Rand.  Eng. 
A:  Min.  Jour.,  Jan.  15  and  29,  1910,  8  pp. 

Mill  of  Randfontein  mine.     Eng.  &  Min.  Jour.,  Nov.  12,  1910,  1  p. 

Recent  improvements  in  cyanide  process  on  Witwatersrand.  Eng.  & 
Min.  Jour.,  July  13,  1907. 

WHITE,  F.  Notes  on  dry-crushing  and  cyaniding  of  Rand  ore.  Inst. 
Min.  &  Met.,  vol.  7,  1898,  21  pp. 

Engineering  and  Mining  Journal.  Cyaniding  at  Ashanti  gold  fields.  Eng. 
&  Min.  Jour.,  Feb.  26,  1910,  1  p. 

Journal  Chemical,  Metallurgical,  and  Mining  Society,  S.  A.  Visit  to 
Simmer  Deep,  Ltd.  May,  1909,  4  pp. 

Mining  and  Scientific  Press.     Cyanidation  in  Transvaal.     (Denny  method.) 
July  20  and  27,  1907,  2  pp.     "Recent  Cyanide  Practice,"  pp.  322  and  325. 
Gold  reduction  plant  on  the  Rand.     Oct.  24,  1903,  1  p. 

South  African  Mining  Journal.  Roodeport  United  Main  Reef  plant. 
July  23,  1910. 

Simmer  Deep  and  Jupiter  plant.     Aug.  1  and  8,  1908,  3  pp. 

Z.  Cyanidation  in  Australia 

ALLEN,  R.  Reduction  plant  and  process  at  Oro-Brownhill  mines,  W.  A. 
M.  &  S.  P.,  Nov.  25  and  Dec.  2,  1905,  3  pp. 

BRAY,  G.  E.  Treatment  of  gold  ores  in  New  Zealand.  N.  Z.  Mines 
Record,  Apr.  16,  1908,  4  pp. 

BROOKE,  H.  J.  Ore  treatment  at  Ivanhoe  mine,  Kalgoorlie.  Eng.  &  Min. 
Jour.,  Oct.  20,  1904,  1  p. 

BROWN,  A.  S.  Metallurgical  practice  in  gold  fields  of  West  Australia. 
Eng.  Mag.,  Jan.,  1909,  17  pp. 

CLAUDET,  A.  C.  South  Kalgurli  Co.  system  of  ore  treatment.  Eng.  & 
Min.  Jour.,  Jan.  20,  1906,  1  p.;  abstract  from  Inst.  Min.  &  Met. 

DRUCKER,  A.  E.  Metallurgical  practice  in  Western  Australia.  M.  &  S. 
P.,  Sept.  24,  1910,  4  pp. 

HACK,  E.  B.  Metallurgical  methods  at  Kalgoorlie,  W.  A.  Eng.  &  Min. 
Jour.,  vol.  75,  p.  150,  2  pp. 

HOOVER,  H.  C.  Ore  treatment  at  Kalgoorlie.  Eng.  &  Min.  Jour.,  Aug. 
15,  1903,  1  p. 

JAMES,  A.  Metallurgical  practice  in  Western  Australia.  Eng.  &  Min. 
Jour.,  Jan.  7,  1904,  1  p. 

MCCONNELL,  J.  Notes  on  dry  and  wet-crushing  with  cyanide  treatment 
in  New  Zealand.  Inst.  Min.  &  Met.,  vol.  7,  1898,  9  pp. 

McMiKF.x,  S.  D.  Milling  practice  at  Komata  reefs  mine,  New  Zealand. 
M.  &  S.  P.,  July  1,  1911,  6  pp. 

MASSON  (J.  R.)  and  EDWARDS  (J.  E.).  Modern  hydrometallurgy  in 
Australia.  Met.  &  Chem.  Eng.,  Oct.,  1910,  3  pp. 


266  TEXT  BOOK  OF  CYANIDE  PRACTICE 

PARKS,  J.  Cyaniding  in  New  Zealand.  T.  A.  I.  M.  E.,  vol.  29,  1899, 
15pp. 

STEPHENS,  F.  B.  Treatment  of  Cassilis  ore.  Eng.  &  Min.  Jour.,  July  29, 
1905,  2  pp.;  abstract  from  Inst.  Min.  &  Met. 

STOKES,  R.  Metallurgical  methods  in  Western  Australia.  Min.  World, 
Jan.  5  and  12,  1907,  4  pp. 

Notes  on  Waihi  ore  treatment.  Jour.  Ch.,  Met.,  &  Min.  Soc.,  S.  A.,  July, 
1907,  4  pp.;  Aug.,  1907,  2  pp.;  Oct.,  1907,  1  p.;  Jan.,  1908. 

VON  BERNE WITZ,  M.  W.  Progress  in  ore  treatment  at  Kalgoorlie.  M.  & 
S.  P.,  June  25,  1910,  3  pp. 

WATT,  E.  O.  Cyanidation  at  Kalgurli  mine,  Kalgoorlie.  Eng.  &  Min. 
Jour.,  Aug.  29,  1903,  2  pp.;  abstract  from  Aust.  Inst.  Min.  Engrs. 

WILLIAMS,  G.  W.  Metallurgy  of  Kalgoorlie  gold  fields.  Eng.  &  Min. 
Jour.,  Feb.  15,  1908,  5  pp. 

Westralian  wet-crushing  plants  with  notes  on  labor  efficiency.  Jour.  Ch., 
Met.,  &  Min.  Soc.,  S.  A.,  Feb.  to  July,  1908,  11  pp.;  Feb.,  1909,  2  pp. 

WINGATE,  H.  Direct  cyaniding  of  wet-crushing  ores  in  New  Zealand. 
T.  A.  I.  M.  E.,  vol.  33,  1902,  13  pp.;  abstract  in  M.  &  S.  P.,  Oct.  11,  1902,  2  pp. 

Engineering  and  Mining  Journal.  Battery  and  cyanide  costs  in  West 
Australia  and  Rand.  Eng.  &  Min.  Jour.,  Apr.  3,  1909. 

Journal  Chamber  of  Mines  of  West  Australia.  Ore  reduction  plants  of 
W.  A.  Nov.  30,  1906,  10  pp. 

Miscellaneous 

ALDERSON,  M.  W.     Aids  to  the  cyanider.     M.  &  S.  P.,  Oct.  15,  1898,  1  p. 

ARGALL,  P.  Mesh  v.  aperture.  Eng.  &  Min.  Jour.,  Nov.  7  and  21;  Dec.  5, 
24,  and  31,  1903. 

Standardization  of  screens.     M.  &  S.  P.,  Dec.  1,  1906,  1  p. 

BENSUSAN,  A.  J.  Passagem  mine  and  works,  Brazil.  Min.  World,  Dec. 
10,  1910,  4  pp.;  Pac.  Miner,  Jan.,  1911,  2  pp.;  abstract  from  Inst.  Min.  & 
Met. 

BISHOP,  L.  D.  Hendryx  methods  of  cyaniding.  West.  Ch.  &  Met., 
Nov.,  1907,  7  pp. 

Boss,  M.  P.  Crushing  ore.  M.  &  S.  P.,  Mar.  14,  1908,  5  pp.  "More 
Recent  Cyanide  Process,"  p.  122. 

BROWNE,  R.  S.  Making  up  of  cyanide  solutions.  Pac.  Miner,  Apr.,  1910, 
3pp. 

The  cyanide  process.  (General  description.)  M.  &  S.  P.,  May  27  and 
June  3,  1905,  2  pp.;  abstract  from  catalog  of  Redwood  Tank  Co. 

BUTTER  WORTH,  G.  B.  Concentration  of  soluble  gold  in  a  cyanide  dump. 
Min.  Mag.,  June,  1910,  1  p. 

BUTTERS,  CHAS.  By-products  in  gold  industry.  Proc.  Ch.  &  Met.  Soc., 
S.  A.,  vol.  2,  1897,  10  pp. 

CAREY,  E.  C.  Amalgamation  vs.  cyanidation.  Mex.  Min.  Jour.,  July, 
1911,  2  pp. 

CHRISTENSEN,  A.  O.  Standard  screen  series  for  laboratory  testing.  Eng. 
&  Min.  Jour.,  July  30,  1910,  1  p. 


CLASSIFIED  BIBLIOGRAPHY  267 

CRANE,  W.  R.  Bibliography  of  cyaniding  ores.  "Index  of  Mining  Engi- 
neering Literature, "  1909,  14  pp.. 

Bibliography  of  metallurgy  of  gold  and  silver.  "Index  of  Mining  Engi- 
neering Literature, "  1909,  4  pp. 

DANCKWARDT,  P.  Relative  merits  of  wet  and  dry  crushing  in  cyanidation. 
M.  &  S.  P.,  Mar.  11,  1905,  1  p. 

DE  KALB,  C.  Standard  screens  for  screen  analysis.  Eng.  &  Min.  Jour., 
July  29,  1905,  1  p. 

DENNY,  G.  A.  Notes  on  reduction  plants  for  gold  and  silver.  Pac.  Miner, 
Nov.,  1910,  2  pp.;  abstract  from  Mex.  Min.  Jour.,  Nov.,  1910,  3  pp. 

DRUCKER,  A.  E.  Costs  at  Usan,  Korea.  M.  &  S.  P.,  Apr.  30,  1910, 
lp. 

Recent  cyanide  practice  in  Korea.  M.  &  S.  P.,  Oct.  3,  1908,  3  pp.  "  More 
Recent  Cyanide  Practice, "  p.  220. 

Recent  milling  practice.  (Korea,  Philippines,  and  India.)  M.  &  S.  P., 
Feb.  19,  1910,  2  pp.  "More  Recent  Cyanide  Practice, "  p.  378. 

DURANT,  H.  T.  Dry-crushing  and  direct  cyaniding.  Mex.  Min.  Jour., 
May,  1911,  1  p. 

GUESS,  H.  A.  Ore  dressing  in  U.  S.  and  Mexico.  Eng.  &  Min.  Jour., 
Oct.  30  and  Nov.  12,  1909,  16  pp. 

GUTHRIE,  G.  L.  Butters  cyanide  plant  at  San  Jacinto,  Honduras.  M.  & 
S.  P.,  June  13,  1908,  2  pp. 

HENDERSON,  E.  T.  Laboratory  screens.  (In  sizing  tests.)  Aust.  Min. 
&  Engr.  Rev.,  Nov.  5,  1908,  3  pp. 

HENDRYX,  W.  A.  Cyanidation  of  ores.  Proc.  Colo.  Sci.  Soc.,  Mar., 
1908,  19  pp.;  Mines  &  Mins.,  vol.  28,  p.  530,  4  pp. 

Cyanidation  of  ores.  (Mechanical  features.)  Met.  &  Chem.  Eng.,  Feb., 
1911,  2  pp. 

HERSAM,  E.  A.  Economy  of  power  in  crushing  ore.  M.  &  S.  P.,  Nov.  16, 
1907,  6  pp.  "More  Recent  Cyanide  Practice,"  p.  20. 

HESS,  C.  W.  Table  for  standardizing  sump  solutions.  M.  &  S.  P.,  Oct.  1, 
1910,  1  p. 

HUNT,  B.     Cyanidation  in  Costa  Rica.     Apr.  21,  1904,  1  p. 

HOOVER,  T.  J.  Standard  series  of  screens  for  laboratory  testing.  Inst. 
Min.  &  Met.,  May,  1910,  23  pp.;  abstract  in  Eng.  &  Min.  Jour.,  July  2,  1910, 
lp. 

JAMES,  A.     Cyanide  practice.     Inst.  Min.  &  Met.,  vol.  3,  1895,  46  pp. 

LOFTS,  H.  F.  Cyanidation  in  Malay  states.  Jour.  Ch.,  Met.,  &  Min. 
Soc.,  S.  A.,  May,  1908,  2  pp. 

MACFARREN,  H.  W.  Amalgamation  methods.  (Referring  to  amalgama- 
tion in  solution.)  M.  &  S.  P.,  Dec.  12,  1908,  3  pp.;  abstract  in  "Mineral 
Industry, "  1908,  vol.  17. 

MEGRAW,  H.  A.  Extraction  percentages  in  metallurgical  plants.  Eng. 
&  Min.  Jour.,  Apr.  2,  1910,  2  pp. 

MERRILL,  C.  W.  Notes  on  alleged  shortage  in  cyanide  bullion.  Inst. 
Min.  &  Met.,  vol.  7,  1899,  6  pp. 

MIERISCH,  B.  Continuous  cyanide  process  without  filters  or  zinc  box. 
Mex.  Min.  Jour.,  Apr.,  1911,  3  pp. 


268  TEXT  BOOK  OF  CYANIDE  PRACTICE 

Proposed  simplification  of  cyanide  process.     Eng.  &  Min.  Jour.,  June  25, 

1910,  2  pp. 

NICOL,  J.  M.  Dynamics  of  cyanide  process.  (Discussion  of  processes 
and  machinery.)  Mex.  Min.  Jour.,  Aug.,  1910,  6  pp. 

PARSONS,  C.  E.  Cyaniding  mill  pulp  after  amalgamation.  M.  &  S.  P., 
May  16,  1908.  "More  Recent  Cyanide  Practice,"  p.  142. 

PARKER,  M.  B.  The  cyanide  process.  Mines  &  Mins.,  vol.  26,  p.  387, 
2pp. 

PUTMAN,  D.  G.  Proposed  simplification  of  cyanide  process.  Eng.  & 
Min.  Jour.,  Nov.  12,  1910,  1  p. 

ROBERTS,  F.  C.     Crushing  and  cyanidation.     Mar.  2  and  30,  1905,  2  pp. 

SHAW,  S.  F.  Mines  and  mills  of  Montezuma  mines,  Costa  Rica.  Eng.  & 
Min.  Jour.,  Oct.  8,  1910,  2  pp. 

Recent  cyanide  practice  at  Montezuma,  Costa  Rica.     M.  &  S.  P.,  Jan.  28, 

1911,  2  pp. 

SMITH,  A.  M.  Amalgamation  in  cyanide  solution.  Pac.  Miner,  Dec., 
1909,  2  pp. 

STEWART,  J.  B.  Suggestions  on  cyanide  practice.  Min.  &  Eng.  World, 
Sept.  23,  1911,  1  p.;  M.  &  S.  P.,  Aug.  26,  1911.  Abstract  from  Bull.  Inst. 
Min.  &  Met. 

SULMAN,  H.  L.  Improvements  in  gold  extraction.  (Cyanidation.)  Inst. 
Min.  &  Met.,  vol.  3,  1895,  60  pp. 

VIRGOE,  W.  H.  The  cyanide  process.  Eng.  &  Min.  Jour.,  vol.  57,  p.  533, 
lp. 

WATT,  O.  E.  Modern  methods  in  ore  treatment  by  cyanidation.  M.  & 
S.  P.,  Aug.  22  to  Sept.  5,  1903,  4  pp. 

Engineering  and  Mining  Journal.  Excessive  wear  on  plates.  (Crushing 
in  solution.)  Dec.  18,  1909. 

Heating  cyanide  solutions.     (Beneficial  results  at  Montana-Tonopah 
mill.)     June  11,  1910. 

Potter  cyanide  process.     Vol.  78,  p.  394,  1  p. 
Standard  screens,  weights,  and  measures.     Mar.  16,  1907,  1  p. 
Use  of  cyanide  tailing  for  stope  filling.     Nov.  12,  1910. 
Journal   Chemical,    Metallurgical,    and   Mining   Society,    S.   A.     Heating 
cyanide  solutions.     Vol.  2,  1809,  6  pp. 

Report   of   subcommittee   on   standardization   of   battery   screening. 
June,  1906,  10  pp. 

Sand  filling  of  stopes  on  Witwatersrand.     (Discussion.)     Sept.,  1910, 
5pp. 

Standardization  of  screens.     (Discussion.)     Sept.  to  Nov.,  1905;  Aug., 
1906,  6  pp. 

Mining  and  Scientific  Press.  Cyanidation  of  ore  containing  both  coarse 
and  fine  gold.  (Views  of  various  experts.)  Dec.  7,  14,  and  21,  1907;  Jan.  11, 
Feb.  8,  May  30,  July  11,  1908.  All  in  "More  Recent  Cyanide  Practice," 
p.  63. 

Standardization  of  screens.     Jan.  12,  1907,  1  p. 


CHAPTER  XX 
TABLES 


10  milli-  =  1  centi-. 
10  centi-  =  1  deci-. 
10  deci-  =  1  (unit). 
10  (units)  =  1  deca-. 


Metric  System  with  Conversions 

10  deca-  =  1  hecto-. 
10  hecto-  =  1  kilo-. 
10  kilo-  =  1  myria-. 

WEIGHT 
Metric  unit  is  gram 


Gram  =  weight  1  cubic  centimeter 
of  water  at  4  °  C. 

Gram  =  15.4324  grains. 

Gram  =  .03215  ounce  troy. 

Gram  =  .00267923  pound  troy. 

Gram  =  .03527    ounce    avoirdupois. 

Gram  =  .00220462  pound  avoirdu- 
pois. 

Milligram  =  .0154324  grain. 

Kilo  or  kilogram  =  32.15  ounces 
troy. 

Kilo  or  kilogram  =  2.67923  pounds 
troy. 

Kilo  or  kilogram  =  35.27  ounces 
avoirdupois. 

Kilo  or  kilogram  =  2.20462  pounds 
avoirdupois. 

Metric  ton  =  1000  kilos  or  kilograms. 

Metric  ton  =  2204.62  pounds  avoir- 
dupois. 

Metric  ton  =  1.10231  United  States 
tons  (2000  pounds). 


Grain  =  .0648  gram. 

Ounce  troy  =  31.10348  grams. 

Pound  troy  =  .37324  kilo  or  kilo- 
gram. 

Pound  troy  =  373.24  grams. 

Ounce  avoirdupois  =  28.3495  grams. 

Pound  avoirdupois  =  .45359  kilo  or 
kilogram. 

Pound  avoirdupois  =  453.59  grams. 

Ton  (2000  pounds)  =  .90718  metric 
ton. 

Ton  (2000  pounds)  =  907.185  kilo- 
grams. 

Assay  ton  =  29.1666  grams. 

Assay  ton  =  .9377  ounce  troy. 

Assay  ton  =  .07814  pound  troy. 

Assay  ton  =  1.0287  ounces  avoirdu- 
pois. 

Assay  ton  =  .0643  pound  avoirdu- 
pois. 


CAPACITY 

Metric  unit  is  liter 


Liter  =  1000  cubic  centimeters. 
Liter  =  .26417     gallon     (231    cubic 

inches). 

Liter  =  1.05668  quarts. 
Liter  =  33.81  liquid  ounces. 
Liter  =  61.023  cubic  inches. 


Gallon  (231  cubic  inches)  =  3.78543 

liters. 
Gallon  (231  cubic  inches)  =  3785.43 

cubic  centimeters. 
Liquid  ounce  =  .029574  liter. 

269 


270 


TEXT  BOOK  OF  CYANIDE  PRACTICE 


VOLUME 


Cubic  meter  =  35.314  cubic  feet. 
Cubic  meter  =  1.3079  cubic  yards. 
Cubic  centimeter  =  .061  cubic  inch. 


Cubic  foot  =  .02832  cubic  meter. 
Cubic  yard  =  .7645  cubic  meter. 


LENGTH 

Metric  unit  is  meter 


Meter  =  39.37  inches. 
Meter  =  3.280833  feet. 
Kilometer  =  3280.833  feet. 
Kilometer  =  .62137  mile. 
Centimeter  =  .3937  inch. 


Inch  =  2.54  centimeters. 
Foot  =  30.48  centimeters. 
Foot  =  .3048  meter. 
Mile  =  1.60935  kilometers. 
Mile  =  1609.347  meters. 


AREA 


Square  meter  =  10.764  square  feet. 

Square  meter  =  1550.3  square  inches. 

Hectare  or  square  hectometer  = 
2.4711  acres. 

Square  kilometer  =  247.1  acres. 

Square  inch  =  6.452  square  centi- 
meters. 


Square  foot  =  929  square  centi- 
meters. 

Square  foot  =  .0929  square  meter. 

Square  mile  =  2.59  square  kilo- 
meters. 

Acre  =  .40469  hectare. 

Acre  =  4046.9  square  meters. 


United  States  Weights  and  Measures 
AVOIRDUPOIS  WEIGHT 


27.34375  grains  =  1  dram. 
16  drams  =  1  ounce  (oz.). 
437.5  grains  =  1  ounce. 
16  ounces  =  1  pound  (lb.). 
7000  grains  =  1  pound. 


100  pounds  =  1  hundredweight. 
2000  pounds  =  1  short  ton  (usually 

used). 
2240  pounds  =  1  long  ton   (seldom 


TROY  WEIGHT 


24  grains  =  1  pennyweight  (dwt.). 
20  pennyweights  =  1  ounce  (oz.). 
480  grains  =  1  ounce. 


12  ounces  =  1  pound  (lb.). 
5760  grains  =  1  pound. 


APOTHECARIES'  WEIGHT 


20  grains  =  1  scruple. 
3  scruples  =  1  dram. 
8  drams  =  1  ounce. 


12  inches  =  1  foot. 
3  feet  =  1  yard. 
5^  yards  =  1  rod. 
16i  feet  =  1  rod. 


480  grains  =  1  ounce. 
12  ounces  =  1  pound. 
5760  grains  =  1  pound. 


LENGTH 


4  rods  =  1  chain. 
66  feet  =  1  chain. 
320  rods  =  1  mile. 
5280  feet  =  1  mile. 


TABLES 


271 


AREA 


144  square  inches  =  1  square  foot. 
9  square  feet  =  1  square  yard. 
30£  square  yards  =  1  square  rod. 


160  square  rods  =  1  acre. 
640  acres  =  1  square  mile. 


VOLUME 
1728  cubic  inches  =  1  cubic  foot.          |  27  cubic  feet 

CAPACITY 
Liquid 

4  gills  =  1  pint. 
2  pints  =  1  quart. 

4  quarts  =  1  gallon  (231  cubic  inches). 
31  £  gallons  =  1  barrel. 
63  gallons  =  1  hogshead. 


1  cubic  yard. 


Dry 

2  pints  =  1  quart. 

4  quarts  =  1  gallon  (268.8025  cubic 

inches). 

2  gallons  =  1  peck. 
4  pecks  =  1   bushel    (2150.42  cubic 

inches). 


AVOIRDUPOIS  AND  TROY  CONVERSIONS 

Ounce  troy  =  1.09714  ounces  avoir- 
dupois. 

Pound  troy  =  13.166  ounces  avoir- 
dupois. 

Pound  troy  =  .822857  pound  avoir- 
dupois. 

Ounce  avoirdupois  =  .91145  ounce 
troy. 


Pound  avoirdupois  =  14.583  ounces 

troy. 
Pound  avoirdupois  =  1.21528  pounds 

troy. 
Ton    (2000    pounds    avoirdupois)  = 

29, 166f  ounces  troy. 
Ton    (2000   pounds    avoirdupois)  = 

2430.56  pounds  troy. 


4  farthings  =  1  penny  (d.). 
4  pence  =  1  shilling  (s.). 
20  shillings  =  1  pound  (£). 
1  pound  =  113.001  grains  gold. 


100  centavos  =  1  peso 

1  peso  =  417.74  grains  silver. 


Money 
ENGLISH 

1  pound  =  7.3224  grams  gold. 
1    pound  =  $4.8665    United    States 
money. 


MEXICAN 


1  peso  =  .87  or  |   troy  ounce 

proximate)  silver. 
1  peso  =  27.073  grams  silver. 


(ap- 


100  cents  =  1  dollar  ($). 


ounce 


1  ounce  troy  =  $20.67. 
1   pennyweight    (dwt.)    = 

troy. 

1  pennyweight  =  $1.03ZV 
1  grain  =  4.306  cents  (United  States). 


UNITED  STATES 

|  1  dollar  =  23.22  grains  gold. 
Value  of  Gold 

1  gram  =  $0.6646. 

.03215  or  -3JT  (approximate) 


1  gram 

ounce  troy. 
1  kilo  =  $664.60. 
1  kilo  =  32.15  ounces  troy. 


272 


TEXT  BOOK  OF  CYANIDE  PRACTICE 


Fahrenheit. 
Centigrade. 


Conversion  of  Thermometer  Readings 

Freezing  Point 

32° 

0° 


Boiling  Point 
212° 
100° 


To  convert  Fahrenheit  to  Centigrade,  subtract  32  and  multiply  by  f . 
To  convert  Centigrade  to  Fahrenheit,  multiply  by  f  and  add  32. 

Weight  and  Measure  of  Water 


1  pound  (avoirdupois)  water  = 

27.68122  cubic  inches. 
1  pound  (avoirdupois)  water  = 

.0160192  cubic  foot. 
1  gallon  (United  States  liquid)  water 

=  231  cubic  inches. 
1  gallon  (United  States  liquid)  water 

=  .13368  cubic  foot. 
1  gallon  (United  States  liquid)  water 

=  3.78543  liters. 


1  gallon  (United  States  liquid)  water 
=  8.3389  pounds  (avoirdupois). 

1  cubic  foot  water  =  62.42  pounds 
(avoirdupois) . 

1  cubic  foot  water  =  7.48052  gallons. 

1  cubic  foot  water  =  28.318  liters. 

1  ton  water  =  239.84  gallons. 

1  ton  water  =  32.041  cubic  feet. 

1  ton  water  =  907.2  liters. 

1  liter  water  =  2.2046  pounds  (avoir- 
dupois). 


Weight  of  Rock  and  Sand 

Cubic  feet 
per  ton. 

Weight  in 
pounds  per 
cubic  foot. 

Sulphide  ore  in  place  

11  to  13 
15  to  18 
14  to  18 
22  to  24 
12 
21 
18 
27 
17 
25 

21.5 
26 
24 

182  to  154 
133  to  111 
143  to  111 
91  to  81 
165 
94 
111 
74 
118 
80 

93 

77 
83.3 

Sulphide  ore  broken 

Oxidized  ore  in  place 

Oxidized  ore  broken 

Quartz  in  place.     (Specific  gravity,  2.65)  
Quartz  broken                     .    .                     

Earth  in  bank                   .        .           .    .    .•  

Earth,  dry  and  loose  .       

Clay  

Loose  sand  

Mill  tailing.*     (Specific  gravity,  2.7) 
Sand  collected  under  water  

Transferred  sand.     (Before  leaching)  

Leached  sand.     (That  has  been  transferred)  . 

*  W.  A.  Caldecott.     Journal  Chemical,  Metallurgical,  and  Mining  Society,  S.  A.,  Oct.,  1908. 
Mining  and  Scientific  Press,  Sept.  24,  1910. 


TABLES 


273 


International  Atomic  Weights,  1911 

Element. 

1 

£ 

A 

J! 

£ 

il 

02 

Element. 

J 

2"w 

Is 

< 

£ 

*i 

"r  *•* 
mm 

Aluminum  
Antimony 

Al 
Sb 
A 
As 
Ba 
Bi 
B 
Br 
Cd 
Cs 
Ca 
C 
Ce 
Cl 
Cr 
Co 
Cb 
Cu 

% 

Eu 
F 
Gd 
Ga 
Ge 
Gl 
Au 
He 
H 
In 
I 
Ir 
Fe 
Kr 
La 
Pb 
Li 
Lu 
Mg 
Mn 
Hg 

27.1 
120.2 
39.88 
74.96 
137.37 
208.0 
11.0 
79.92 
112.40 
132.81 
40.09 
12.0 
140.25 
35.46 
52.0 
58.97 
93.5 
63.57 
162.5 
167.4 
152.0 
19.0 
157.3 
69.9 
72.5 
9.1 
197.2 
3.99 
1.008 
114.8 
126.92 
193.1 
55.85 
82.92 
139.0 
207.10 
6.94 
174.0 
24.32 
54.93 
200.0 

2.56 
6.71 

9.83 

8.65 
1.58 

5.0 
8.5 

8.9 

19.32 

22.42 
7.45 

1.37 

1.75 
8. 
3.59 

Molybdenum.  .  . 
Neodymium  .  .  . 
Neon 

Mo 
Md 

Ne 
Ni 
N 
Os 
O 
Pd 
P 
Pt 
K 
Pr 
Ra 
Rh 
Rb 
Ru 
Sa 
Sc 
Se 
Si 
Ag 
Na 
Sr 
S 
Ta 
Te 
Tb 
Tl 
Th 
Tm 
Sn 
Ti 
W 
U 
V 
Xe 
Yb 
Yt 
Zn 
Zr 

96.0 
144.3 
20.2 
58.68 
14.01 
190.9 
16.0 
106.7 
31.04 
195.2 
39.10 
140.6 
226.4 
102.9 
85.45 
101.7 
150.4 
44.1 
79.2 
28.3 
107.88 
23.0 
87.63 
32.07 
181.0 
127.5 
159.2 
204.0 
232.4 
68.5 
119.0 
48.1 
184.0 
238.5 
51.06 
30.2 
72.0 
89.0 
65.37 
90.6 

8.8 

21.5 
0.865 

10.505 
0.97 

7.35 
17.03 

6.86 

\reron 

Arsenic  
Barium  
Bismuth  
Boron  
Bromine  

Nickel 

Nitrogen  . 

Osmium.  . 

Oxygen  

Palladium  
Phosphorus  .... 
Platinum  
Potassium  
Praseodymium 
Radium  
Rhodium  
Rubidium  
Ruthenium.  .  .  . 
Samarium 

Cadmium  

CsBsium. 

Calcium 

Carbon  
Cerium  
Chlorine  
Chromium  
Cobalt     . 

Columbium.  .  .  . 
Copper  
Dysprosium  
Erbium 

Scandium  
Selenium  
Silicon 

Europium 

Silver 

Fluorine 

Sodium  
Strontium  . 

jradolinium.  .  .  . 
jrallium  
aermanium.  .  .  . 
Glucinum  

Sulphur  
Tantalum  
Tellurium  

Gold  
rlelium 

Terbium  
Thallium 

rlydrogen  
Indium  

Thorium  
Thulium  
Tin 

Iodine 

Iridium 

Titanium 

'ron  . 
krypton  
lanthanum.  .  .  . 
^ead  
Lithium  

Tungsten 

Uranium  
Vanadium  
Xenon  
Ytterbium  
Yttrium 

jutecium 

Magnesium.  .  .  . 
Vlanganese  
Mercury  

•Zinc     . 

Zirconium  

274  TEXT  BOOK  OF  CYANIDE  PRACTICE 

Maximum  Solubilities 
(In  water  at  ordinary  temperatures) 

Aluminum  sulphate  (Al 2(804)3) .1  part  in  3  parts  of  water. 

Calcium  carbonate  (CaCO3) Insoluble. 

Calcium  chloride  (CaCl2) 1  part  in    1£  parts  of  water. 

Calcium  hydroxide  (slacked  lime— Ca(OH)2)..l        "    600  "   " 

Calcium  oxide  (unslacked  lime — CaO) 1        "    800  "    " 

Calcium  sulphate  (CaSO4) 1        "    500  "   " 

Calcium  sulphite  (CaSO3) Insoluble. 

Copper  sulphate  (CuSO4) 1  part  in  4  parts  of  water. 

Iron  oxide,  hydroxide,  and  sulphide Insoluble. 

Iron  sulphate  (copperas — FeSO4) 1  part  in  4  parts  of  water. 

Lead  acetate  (Pb(C2H3O2)2) 1        "      2 

Lead  carbonate  (PbCO3) Insoluble. 

Lead  oxide  (litharge — PbO) " 

Lead  sulphate  (PbSO4) 

Lead  sulphite  (PbSO3) 

Lead  chloride  (PbCl2) 1  part  in  93  parts  of  water. 

Magnesium  sulphate  (MgSO4) 1        "        3  "   " 

Mercuric  chloride  (HgCl2) 1        "      15 

Oxalic  acid  (C2O4H2.2  H2O) 1        "      10|         "  " 

Potassium  bicarbonate  (KHCO3) 1        "        3 

Potassium  carbonate  (K2CO3) 1        "        1  part      " 

Potassium  cyanide  (KCN) 1        "          f         "   "  (boiling). 

Potassium  ferrocyanide  (K4Fe(CN)6) 1        "        3|  parts    " 

Potassium  hydroxide  (KOH) 1        "        1  part      " 

Potassium  iodide  (KI) 1        "          f          "  " 

Potassium  sulphate  (K2SO4) 1        "        9  parts     " 

Silver  nitrate  (AgNO3) 1        "         ^T  part   " 

Sodium  bicarbonate  (NaHCO3) 1        "      10  parts     " 

Sodium  bisulphate  (NaHSO4) 1        "        3|         "  " 

Sodium  carbonate  (Na2CO3) 1        "        4          "    " 

Sodium  hydroxide  (NaOH) 1        "        1  part      " 

Sodium  sulphate  (Na2SO4) 1        "        4  parts    " 

Zinc  carbonate  (ZnC03) Insoluble. 

Zinc  cyanide  (Zn(CN)i) " 

Zinc  hydroxide  (Zn(OH)2) " 

Zinc  sulphate  (Zn(SO)4) 1  part  in  If  parts  of  water. 

Formulae  for  Circles  and  Circular  Tanks 

Circumference  of  circle  =  diameter  X  3.1416. 

,    .    .        /  diameter  V  ^, 
Area  of  circle  =  I -= 1   X  3.1416. 

Volume  of  cylindrical  tank  =  area  of  bottom  X  height. 

,7  .  area  of  base  X  height 

Volume  of  cone  =  — —  — 


TABLES 


275 


Capacity  of  Circular  Tanks  per  Foot  of  Depth 

(1  ton  water  =  32  cubic  feet) 

Interpolate  intermediate  values. 

To  find  capacity  of  tank,  multiply  capacity  for  1  foot  of  depth,  as  given  in 

;he  table,  by  depth  of  tank  in  feet. 

To  find  capacity  of  tanks  larger  than  given  in  the  table,  multiply  by  4  the 

value,  as  given  in  the  table,  for  a  tank  one-half  the  given  diameter,  or 

multiply  by  9,  the  value  as  given,  for  a  tank  one-third  the  given  diameter. 

To  find  gallons  in  tank,  multiply  capacity  in  cubic  feet  by  7.48,  or  tons  of 

water  by  239.84. 

Diameter 
of  Tank. 

Cu.  Ft. 
Capac- 
ity or 
Area  in 
Sq.  Ft. 

Capac- 
ity in 
Tons  of 
Water. 

Diameter 
of  Tank. 

Cu.  Ft. 
Capac- 
ity or 
Area  in 
Sq.  Ft. 

Capac- 
ity in 
Tons  of 
Water. 

Diameter 
of  Tank. 

Cu.  Ft. 
Capac- 
ity or 
Area  in 
Sq.  Ft. 

Capac- 
ity in 
Tons  of 
Water. 

Ft. 

In. 

Ft. 

In. 

Ft. 

In. 

5 

19.63 

.614 

14 

6 

165.13 

5.16 

24 

452.39 

14.137 

5 

3 

21.65 

.677 

14 

9 

170.87 

5.34 

24 

3 

461.86 

14.433 

5 

6 

23.76 

.743 

15 

176.71 

5.522 

24 

6 

471.44 

14.733 

5 

9 

25.97 

.812 

15 

3 

182.65 

5.708 

24 

9 

481.11 

15.035 

6 

28.27 

.883 

15 

6 

188.69 

5.897 

25 

490.87 

15.34 

6 

3 

30.68 

.959 

15 

9 

194.83 

6.088 

25 

3 

500.74 

15.648 

6 

6 

33.18 

.037 

16 

201.06 

6.283 

25 

6 

510.71 

15.96 

6 

9 

35.78 

.118 

16 

3 

207.39 

6.481 

25 

9 

520.77 

16.274 

7 

38.48 

.203 

16 

6 

213.82 

6.682 

26 

530.93 

16.592 

7 

3 

41.28 

.29 

16 

9 

220.35 

6.886 

26 

3 

541.19 

16.912 

7 

6 

44.18 

.381 

17 

226.98 

7.093 

26 

6 

551.55 

17.236 

7 

9 

47.17 

.474 

17 

3 

233.71 

7.303 

26 

9 

562. 

17.563 

8 

50.27 

.571 

17 

6 

240.53 

7.517 

27 

572.56 

17.892 

8 

3 

53.46 

1.671 

17 

9 

247.45 

7.733 

27 

3 

583.21 

18.225 

8 

6 

56.75 

1.773 

18 

254.47 

7.952 

27 

6 

593.96 

18.561 

8 

9 

60.13 

1.879! 

18 

3 

261.59 

8.175 

27 

9 

604.81 

18.9 

9 

63.62 

1.988 

18 

6 

268.80 

8.4 

28 

615.75 

19.242 

9 

3 

67.20 

2.1 

18 

9 

276.12 

8.629 

28 

3 

626.80 

19.588 

9 

6 

70.88 

2.215 

19 

283.53 

8.86 

28 

6 

637.94 

19.936 

9 

9 

74.66 

2.333 

19 

3 

291.04 

9.095 

28 

9 

649.18 

20.287 

10 

78.54 

2.454 

19 

6 

298.65 

9.333 

29 

660.52 

20.641 

10 

3 

82.52 

2.579 

19 

9 

306.35 

9.573 

29 

3 

671.96 

20.999 

10 

6 

86.59 

2.706 

20 

314.16 

9.818 

29 

6 

683.49 

21.359 

10 

9 

90.76 

2.836 

20 

3 

322.06 

10.064 

29 

9 

695.13 

21.723 

11 

95.03 

2.97 

20 

6 

330.06 

10.314 

30 

706.86 

22.089 

11 

3 

99.4 

3.106 

20 

9 

338.16 

10.568 

30 

3 

718.69 

22.459 

11 

6 

103.87 

3.246 

21 

346.36 

10.824 

30 

6 

730.62 

22.832 

11 

9 

108.43 

3.388 

21 

3 

354.66 

11.083 

30 

9 

742.64 

23.208 

12 

113.1 

3.534 

21 

6 

363.05 

11.345 

31 

754.77 

23.587 

12 

3   117.86 

3.683 

21 

9 

371.54 

11.611 

31 

3 

766.99 

23.968 

12 

6    122.72 

3.835 

22 

380.13 

11.879 

31 

6 

779.31 

24.353 

12 

9    127.68 

3.99 

22 

3 

388.82 

12.151 

31 

9 

791.73 

24.741 

13 

132.73 

4.148 

22 

6 

397.61 

12.425 

32 

804.25 

25.133 

13 

3    137.89 

4.309 

22 

9 

406.49 

12.703 

32 

3 

816.86 

25.527 

13 

6    143.14 

4.473 

23 

415.48 

12.984 

32 

6 

829.5825.922 

13 

9    148.49 

4.64 

23 

3 

424.56 

13.268 

32 

9 

842.39  26.325 

14 

153.94 

4.811 

23 

6 

433.74 

13.554 

33 

855.30 

26.728 

14 

3  1159.48 

4.984 

23 

9 

443.01 

13.844 

33 

3 

868.31 

27.135 

276 


TEXT  BOOK  OF  CYANIDE  PRACTICE 


Slime  Pulp  Table  * 

Specific  gravity  of  dry  slime,  2.7.     Upper  set  of  figures. 
Specific  gravity  of  dry  slime,  2.5.     Lower  set  of  figures. 
Single  set  of  figures  refer  to  any  specific  gravity. 

Specific 
Gravity 
of  Slime 
Pulp. 

Per  Cent  by 
Weight  of 
Dry  Slime 
in  Wet 
Pulp. 

Per  Cent  by 
Weight  of 
Solution  in 
Wet  Pulp. 

Ratio  by 
Weight  of 
Solution 
to  1  of 
Dry 
Slime. 

Volume  in 
Cu.  Ft.  of 
1  Ton  Wet 
Pulp. 

Weight  in 
Lbs.  of  1 
Cu.  Ft.  of 
Wet  Pulp. 

Volume  in 
Cu.  Ft.  of 
Wet  Pulp 
Containing 
1  Ton  Dry 
Slime. 

Weight  in 
Lbs.  of  Dry 
Slime  in  1 
Cu.  Ft. 
Wet  Pulp. 

1.00 

00 

100 

32 

62.5 

00 

1.01 

1.57 

1.65 

98.43 
98.35 

62.63 
59.61 

31.68 

63.12 

2015 
1920 

.99 
1.04 

1.02 

3.11 
3.27 

96.89 
96.73 

31.13 

29.58 

31.37 

63.75 

1007.5 
959.29 

1.98 

2.08 

1.03 

4.63 

4.85 

95.37 
95.15 

20.63 
19.62 

31.07 

64.37 

671.66 
640.66 

2.98 
3.13 

1.04 

6.11 
6.41 

93.89 
93.59 

15.38 
14.60 

30.77 

65.00 

503.75 
480.01 

3^97 
4.17 

1.05 

7.56 
7.94 

92.44 
92.06 

12.23 
11.59 

30.48 

65.62 

403 
383.74 

4.96 
5.21 

1.06 

8.99 
9.43 

91.01 
90.57 

10.13 
9.60 

30.19 

66.25 

335.83 
320.01 

5.95 
6.25 

1.07 

10.39 
10.90 

89.61 
89.10 

8.63 

8.17 

29.91 

66.87 

287.86 
275.27 

6.95 
7.30 

1.08 

11.76 
12.35 

88.24 
87.65 

7.50 
7.10 

29.63 

67.50 

251.87 
240 

7.94 
8.34 

1.09 

13.11 
13.76. 

86.89 
86.24 

6.63 
6.27 

29.36 

68.12 

223.89 
213.45 

8.93 
9.38 

1.10 

14.44 
15.15 

85.56 

84.85 

5.93 
5.60 

29.09 

68.75 

201.50 
191.99 

9.92 
10.42 

1.11 

15.74 
16.51 

84.26 
83.49 

5.36 
5.06 

28.83 

69.37 

183.18 
174.71 

10.92 
11.47 

1.12 

17.01 
17.86 

82.98 
82.14 

4.88 
4.60 

28.57 

70 

167.92 
159.99 

11.91 
12.51 

1.13 

18.27 
19.17 

81.73 
80.83 

4.48 
4.22 

28.32 

70.62 

155 
147.83 

12.90 
13.55 

1.14 

19.50 
20.47 

80.50 
79.53 

4.13 
3.89 

28.07 

71.25 

143.93 
137.26 

13.89 
14.59 

*  In  part  from  W.  A.  Caldecott.    Proc.  Chemical  and  Metallurgical  Society,  S.  A.    Vol.  2. 


TABLES 


277 


Slime  Pulp  Table*  —  Continued 

Specific  gravity  of  dry  slime,  2.7.     Upper  set  of  figures. 
Specific  gravity  of  dry  slime,  2.5.     Lower  set  of  figures. 
Single  set  of  figures  refer  to  any  specific  gravity. 

Specific 
Gravity 
of  Slime 
Pulp. 

Per  Cent  by 
Weight  of 
Dry  Slime 
in  Wet 
Pulp. 

Per  Cent  by 
Weight  of 
Solution  in 
Wet  Pulp. 

Ratio  bv 
Wreight  of 
Solution 
tolof 
Dry 
Slime. 

Volume  in 
Cu.  Ft.  of 
1  Ton  Wet 
Pulp. 

Weight  in 
Lbs.  of  1 
Cu.  Ft.  of 
Wet  Pulp. 

Volume  in 
Cu.  Ft.  of 
Wet  Pulp 
Containing 
I  Ton  Dry 
Slime. 

Weight  in 
Lbs.  of  Dry 
Slime  in  1 
Cu.  Ft. 
Wet  Pulp. 

1.15 

20.71 

21.74 

79.29 
78.26 

3.83 
3.60 

27.83 

71.87 

134.33 
128.02 

14.89 
15.63 

1.16 

21.90 
22.99 

78.10 
77.01 

3.56 
3.35 

27.59 

72.50 

125.94 
120.02 

15.88 
16.67 

1.17 

23.07 
24.22 

76.93 

75.78 

3.34 
3.13 

27.35 

73.12 

118.53 
112.96 

16.87 
17.71 

1.18 

24.22 
25.42 

75.78 
74.58 

3.13 
2.93 

27.12 

73.75 

111.94 
106.58 

17.86 
18.75 

1.19 

25.35 
26.61 

74.65 
73.39 

2.95 
2.76 

26.89 

74.37 

106.05 
101.11 

18.86 
19.80 

1.20 

26.47 

27.77 

73.53 
72.23 

2.78 
2.60 

26.67 

75 

100.75 
96.01 

19.85 
20.84 

1.21 

27.56 

28.92 

72.44 

71.08 

2.63 
2.46 

26.45 

75.62 

95.95 
91.52 

20.84 

21.88 

1.22 

28.64 
30.05 

71.36 
69.95 

2.49 
2.33 

26.23 

76.25 

91.59 
87.35 

21.84 
22.93 

1.23 

29.69 
31.17 

70.31 
68.83 

2.37 
2.21 

26.02 

76.87 

87.61 
83.52 

22.83 
23.97 

1.24 

30.74 
32.26 

69.26 
67.74 

2.25 
2.10 

25.81 

77.50 

83.96 
80.01 

23.82 
25.01 

1.25 

31.76 
33.33  ' 

68.24 
66.67 

2.15 
2.00 

25.60 

78.12 

80.60 
76.80 

24.81 
26.05 

1.26 

32.77 

34.39 

67.23 
65.61 

2.05 
1.91 

25.39 

78.76 

77.50 

73.88 

25.81 
27.10 

1.27 

33.76 
35.43 

66.24 
64.57 

1.96 
1.82 

25.19 

79.37 

74.63 
71.10 

•    26.80 
28.14 

1.28 

34.74 
36.46 

65.26 
63.54 

1.88 
1.74 

25 

80 

71.96 
68.50 

27.79 
29.18 

1.29 

35!  70 

37  .  47 

64.30 
|     62.53 

1.80 
1.67 

24.81 

80.62 

69.48 
66.24 

28.78 
30.22 

*  In  part  from  W.  A.  Caldecott.    Proc.  Chemical  and  Metallurgical  Society,  S.  A.     Vol.  2. 


278 


TEXT  BOOK  OF  CYANIDE  PRACTICE 


Slime  Pulp  Table  *  —  Continued 

Specific  gravity  of  dry  slime,  2.7.     Upper  set  of  figures. 

Specific  gravity  of  dry  slime,  2.5.     Lower  set  of  figures. 

Single  set  of  figures  refer  to  any  specific  gravity. 

Specific 
Gravity 
of  Slime 
Pulp. 

Per  Cent  by 
Weight  of 
Dry  Slime 
in  Wet 
Pulp. 

Per  Cent  by 
Weight  of 
Solution  in 
Wet  Pulp. 

Ratio  by 
Weight  of 
Solution 
to  1  of 
Dry 
Slime. 

Volume  in 
Cu.  Ft.  of 
1  Ton  Wet 
Pulp. 

Weight  in 
Lbs.  of  1 
Cu.  Ft.  of 
Wet  Pulp. 

Volume  in 
Cu.  Ft.  of 
Wet  Pulp 
Containing 
1  Ton  Dry 
Slime. 

Weight  in 
Lbs.  of  dry 
Slime  in  1 
Cu.  Ft. 
Wet  Pulp. 

1.30 

36.65 

63.35 

1.73 

24.62 

81.25 

67.17 

29.78 

38.46 

61.54 

1.60 

64.01 

31.27 

1.31 

37.58 

62.42 

1.66 

24.43 

81.87 

65 

30.77 

39.44 

60.56 

1.54 

62.05 

32.30 

1.32 

38.50 

61.50 

1.60 

24.24 

82.50 

62.97 

31.76 

40.40 

59.60 

1.48 

60.12 

33.34 

1.33 

39.40 

60.60 

1.54 

24.06 

83.12 

61.06 

32.76 

41.35 

58.65 

1.42 

58.23 

34.38 

1.34 

40.29 

59.71 

1.48 

23.88 

83.75 

59.26 

33.75 

42.29 

57.71 

1.36 

56.47 

35.42 

1.35 

41.17 

58.83 

1.43 

23.70 

84.37 

57.57 

34.74 

43.21 

56.79 

1.31 

54.86 

36.46 

1.36 

42.04 

57.96 

1.38 

23.53 

85 

55.97 

35.73 

44.12 

55.88 

1.27 

53.34 

37.50 

1.37 

42.89 

57.11 

1.33 

23.36 

85.62 

54.46 

36.73 

45.01 

54.99 

1.22 

51.90 

38.54 

1.38 

43.73 

56.27 

1.29 

23.19 

86.25 

53.03 

37.72 

45.89 

54.11 

1.18 

50.55 

39.58 

1.39 

44.56 

54.44 

1.25 

23.02 

86.87 

51.67 

38.71 

46.77 

53.23 

1.14 

49.26 

40.63 

1.40 

45.37 

54.63 

1.21" 

22.86 

87.50 

50.37 

39.70 

47.62 

52.38 

1.10 

48.01 

41.67 

1.41 

46.18 

53.82 

1.17 

22.70 

88.12 

49.15 

40.70 

48.46 

51.54 

1.06 

46.84 

42.71 

1.42 

46.97 

53.03 

1.13 

22.54 

88.75 

47.98 

41.69 

49.30 

50.70 

1.03 

45.72 

43.75 

1.43 

47.75 

52.25 

1.10 

22.38 

89.37 

46.86 

42.68 

50.12 

49.88 

1.00 

44.66 

44.79 

1.44 

48.52 

51.48 

1.06 

22.22 

90 

45  .SO 

43.67 

50.93 

49.07 

.96 

43.65 

45.82 

*  In  part  from  W.  A.  Caldecott.    Proc.  Chemical  and  Metallurgical  Society,  S.  A.    Vol.  2. 


TABLES 


279 


Slime  Pulp  Table*  —  Continued 

Specific  gravity  of  dry  slime,  2.7.     Upper  set  of  figures. 
Specific  gravity  of  dry  slime,  2.5.     Lower  set  of  figures. 
Single  set  of  figures  refer  to  any  specific  gravity. 

Specific 
Gravity 
of  Slime 
Pulp. 

Per  Cent  by 
Weight  of 
Dry  Slime 
in  Wet 
Pulp. 

Per  Cent  by 
Weight  of 
Solution  in 
Wet  Pulp. 

Ratio  by 
Weight  of 
Solution 
tolof 
Dry 
Slime. 

Volume  in 
Cu.  Ft.  of 
1  Ton  Wet 
Pulp. 

Weight  in 
Lbs.  of  1 
Cu.  Ft.  of 
Wet  Pulp. 

Volume  in 
Cu.  Ft.  of 
Wet  Pulp 
Containing 
1  Ton  Dry 
Slime. 

Weight  in 
Lbs.  of  Dry 
Slime  in  1 
Cu.  Ft. 
Wet  Pulp. 

1.45 

49.28 
51.72 

50.72 
48.28 

1.03 
.93 

22.07 

90.62 

44.78 
42.68 

44.67 

46.87 

1.46 

50.03 
52.51 

49.97 
47.49 

1.00 
.90 

21.92 

91.25 

43.88 
41.82 

45.66 
47.91 

1.47 

50.77 
53.29 

49.23 
46.71 

.97 

.88 

21.77 

91.87 

42.87 
40.86 

46.65 
48,95 

1.48 

51.50 
54.05 

48.50 
45.95 

.94 

.85 

21.62 

92.50 

41.98 
40 

47.65 
50 

1.49 

52.22 
54.81 

47.78 
45.19 

.92 

.82 

21.48 

93.12 

41.12 
39.19 

48.64 
51.04 

1.50 

52.93 
55.56 

47.07 
44.44 

.89 
.80 

21.33 

93.75 

40.30 
38.41 

49.63 
52.08 

1.51 

53.63 
56.29 

46.37 
43.71 

.87 
.78 

21.19 

94.37 

39.51 
37.65 

50.62 
53.12 

1.52 

54.33 
57.02 

45.67 
42.98 

.84 
.75 

21.05 

95 

38.75 
36.93 

51.62 
54.17 

1.53 

55.01 
57.73 

44.99 
42.27 

.82 
.73 

20.92 

95.62 

38.02 
36.23 

52.61 
55.21 

1.54 

55.68 
58.44 

44.32 
41.56 

.80 
.71 

20.78 

96.25 

37.31 
35.56 

53.60 
56.25 

1.55 

56.35 
59.14 

43.65 
40.86 

.78 
.69 

20.65 

96.87 

36.64 
34.92 

54.59 
57.29 

1.56 

57.01 
59.83 

42.99 
40.17 

.76 
.67 

20.51 

97.50 

35.98 
34.29 

55.59 
58.33 

1.57 

57.65 
60.51 

42.35 
39.49 

.74 
.65 

20.38 

98.12 

35.35 
33.69 

56.58 
59.37 

1.58 

58.29 
61.18 

41.71 

38.82 

.72 
.63 

20.25 

98.75 

34.74 
33.11 

57.57 
60.42 

1.59 

58.93 
61.84 

41.07 
38.16 

.70 
.62 

20.13 

99.37 

34.15 
32.54 

58.56 
61.46 

In  part  from  W.  A.  Caldecott.    Proc.  Chemical  and  Metallurgical  Society,  S.  A.    Vol.  2. 


280 


TEXT  BOOK  OF  CYANIDE  PRACTICE 


Slime  Pulp  Table*  —  Continued 

Specific  gravity  of  dry  slime,  2.7.     Upper  set  of  figures. 
Specific  gravity  of  dry  slime,  2.5.     Lower  set  of  figures. 
Single  set  of  figures  refer  to  any  specific  gravity. 

Specific 
Gravity 
of  Slime 
Pulp. 

Per  Cent  by 
Weight  of 
Dry  Slime 
in  Wet 
Pulp. 

Per  Cent  by 
Weight  of 
Solution  in 
Wet  Pulp. 

Ratio  by 
Weight  of 
Solution 
to  1  of 
Dry 
Slime. 

Volume  in 
Cu.  Ft.  o 
1  Ton  Wet 
Pulp. 

Weight  in 
Lbs.  of  1 
Cu.  Ft.  o 
Wet  Pulp 

Volume  in 
Cu.  Ft.  of 
Wet  Pulp 
Containing 
1  Ton  Dry 
Slime. 

Weight  in 
Lbs.  of  Dry 
Slime  in  1 
Cu.  Ft. 
Wet  Pulp. 

1.60 

59.55 
62.50 

40.45 
37.50 

.68 

.60 

20 

100 

33.58 
32 

59.56 

62.50 

1.61 

60.17 
63.15 

39.83 
36.85 

.66 

.58 

19.88 

100.62 

33.03 
31.48 

60.55  > 
63.54 

1.62 

60.78 
63.79. 

39.22 
36.21 

.65 
.57 

19.75 

101.25 

32.50 
30.97 

61.54 
64.59 

1.63 

61.38 
64.42 

38.62 
35.58 

.63 
.55 

19.63 

101.87 

31.98 
30.48 

62.54 
65.63 

1.64 

61.97 
65.04 

38.03 
34.96 

.61 
.54 

19.51 

102.50 

31.48 
30 

63.53 
66.67 

1.65 

62.56 
65.66 

37.44 
34.34 

.60 
.52 

19.39 

103.12 

31 
29.54 

64.52 
67.72 

1.66 

63.14 

66.27 

36.86 
33.73 

.58 
.51 

19.28 

103.75 

30.53 
29.10 

65.51 
68.76 

1.67 

63.71 

66.87 

36.29 
33.13 

.57 
.50 

19.16 

104.37 

30.07 
28.66 

66.51 
69.80 

1.68 

64.28 
67.46 

35.72 
32.54 

.56 

.48 

19.05 

105 

29.63 
28.24 

67.50 
70.84 

1.69 

64.84 
68.05 

35.16 
31.95 

.54 
.47 

18.93 

105.62 

29.20 
27.83 

68.49 
71.88 

1.70 

65.39 
68.63 

34.61 
31.37 

.53 
.46 

18.82 

106.25 

28.79 
27.44 

69.48 
72.93 

1.71 

65.93 
69.20 

34.07 
30.80 

.52 
.45 

18.71 

106.87 

28.38 
27.05 

70.48 
73.97 

1.72 

66.47 
69.77 

33.53 
30.23 

.50 
.43 

18.61 

107.50 

27.99 
26.67 

71.47 
75.01 

1.73 

67.02 
70.33 

32.98 
29.67 

.49 
.42 

18.50 

108.13 

27.60 
26.31 

72.46 
76.04 

1.74 

67.56 

70.88 

32.44 
29.12 

.48 
.41 

18.39 

108.75 

27.22 
25.95 

73.45 

77.08 

In  part  from  W.  A.  Caldecott.    Proc.  Chemical  and  Metallurgical  Society,  S.  A.    Vol.  2. 


TABLES 


281 


Slime  Pulp  Table  *  —  Concluded 

Specific  gravity  of  dry  slime,  2.7.     Upper  set  of  figures. 
Specific  gravity  of  dry  slime,  2.5.     Lower  set  of  figures. 
Single  set  of  figures  refer  to  any  specific  gravity. 

Specific 
Gravity 
of  Slime 
Pulp. 

Per  Cent  by 
Weight  of 
Dry  Slime 
in  Wet 
Pulp. 

Per  Cent  by 
Weight  of 
Solution  in 
Wet  Pulp. 

Ratio  by 
Weight  of 
Solution 
tolof 
Dry 
Slime. 

Volume  in 
Cu.  Ft.  of 
1  Ton  Wet 
Pulp. 

Weight  in 
Lbs.  of  1 
Cu.  Ft.  of 
Wet  Pulp. 

Volume  in 
Cu.  Ft.  of 
Wet  Pulp 
Containing 
1  Ton  Dry 
Slime. 

Weight  in 
Lbs.  of  Dry 
Slime  in  1 
Cu.  Ft. 
Wet  Pulp. 

1.75 

68.07 

71.43 

31.93 
28.57 

.47 

.40 

18.29 

109.38 

26.86 
25.61 

74.45 
78.13 

1.76 

68.58 
71.97 

31:42 
28.03 

.46 
.39 

18.18 

110 

26.51 
25.26 

75.44 
79.17 

1.77         69.09 
72.50 

30.91 
27.50 

.45 

.38 

18.08 

110.63 

26.16 
24.93 

76.43 
80.21 

1.78 

69.60 
73.03 

30.40 
26.97 

.44 
.37 

17.98 

111.25 

25.83 
24.61 

77.43 
81.25 

1.79 

70.10 
73.56 

29.90 
26.44 

.43 
.36 

17.88 

111.88 

25.50 
24.30 

78.42 
82.29 

1.80 

70.59 
74.07 

29.41 
25.93 

.42 
.35 

17.78 

112.50 

25.19 
24 

79.41 
83.33 

1.81 

71.08 
74.58 

28.92 
25.42 

.41 
.34 

17.68 

113.13       24.88 
!    23.71 

80.40 
84.37 

1.82 

71.56 
75.09 

28.44 
24.91 

.41 
.33 

17.58 

113.75 

24.57 
23.41 

81.40 
85.41 

1.83     !     72.04 
75.59 

27.96 
24.41 

.39         17.48 
.32     1 

114.38 

24.27 
23.13 

82.39 
86.46 

1.84 

72.51 
76.09 

27.49 
23.91 

.38 
.31 

17.39 

115 

24 
22.86 

83.38 
87.50 

1.85         72.97 
76.58 

27.03 
23.42 

.37 
.31 

17.30 

115.63 

23.70 
22.59 

84.37 
88.54 

1.86         73.43 
77.06 

26.57 
22.94 

.36 
.30 

17.20 

116.25 

23.43 
22.33 

85.37 
89.58 

1.87         73.89 
77.54 

26.11 
22.46 

.35         17.11 
.29 

116.88       23.15 
22.07 

86^36 
90.63 

1.88     :     74.34 
78.01 

25.66 
21.99 

.35         17.02      117.50       22.89 
.28                                        21.83 

87.35 
91.67 

1.89         74.79 

78.48 

25.21 
21.52 

.34 
.27 

16.93 

118.13 

22.64 
21.57 

88.35 
92.71 

1.90         75.23 
78.95 

1.91         75.67 
79.41 

24.77 
21.05 

24.33 
20.59 

.33 

.27 

.32 
.26 

16.84 
16.75 

118.75 
119.38 

22.40 
21.32 

22.14 
21.10 

89.34 
93.75 

90.33 
94.79 

1.92         76.10 

79.86 

23.90 
20.14 

.31         16.67     120            20.90 
.25                                         20.87 

91.32 
95.83 

*  In  part  from  W.  A.  Caldecott.    Proc.  Chemical  and  Metallurgical  Society,  S.  A.    Vol.  2. 


INDEX 


A. 

Acid  cyanide  solutions,  34. 

Acidity    of    cyanide    solutions,    test 

for,  33. 
Acid  slag,  185,  190. 

solutions,     standard.     (See     Solu- 
tions.) 

treatment.     (See  Precipitate.) 
treatment    and    roasting,    chapter 

on,  179. 

treatment     of     concentrate,     pre- 
liminary, 23,  204. 
Adair-Usher  cyanide  process,  129. 
Aeration,  11,  13,  47,  57,  58,  93,  96, 

102,  103,  199. 
method  in  percolation,   102,   104, 

199. 
Agitation,  113. 

amount  and  strength  of  solution, 

114. 

and  slime  treatment,  108. 
extraction  tests,  71. 
increased  consumption  of  cyanide 

and  lime,  124. 

intermittent  and  continuous,  115. 
of  concentrate,  201. 
Agitators  for  laboratory,  71. 
Agitators,  types  of,  118. 
Alkaline  sulphides  or  sulphocyanides 

in  silver  ore,  19,  46. 
sulphides    or   sulphocyanides,    oc- 
currence, 23,  24,  45. 
sulphides  and  sulphocyanides,  re- 
moval by  lead  acetate,  46,  47. 
sulphides  and  sulphocyanides,  re- 
moval by  mercury,  13,  25,  47, 
171. 

sulphides  and  sulphocyanides,  re- 
moval by  zinc,  46. 
sulphides,  test  for,  48. 
Alkalinity  and  lime,  chapter  on,  54. 
A  Ik- Alia  and  alkalinity.     (See  Lime.) 


Alkali  solutions,  standard.     (See  So- 
lutions.) 

Aluminum,  effect  of,  26. 

Amalgamation  of  concentrate,  201. 
tests,  77. 

Ammonia,  use  in  cyaniding,  23. 

Ammonium  cyanide,  9. 

Annealing  graphite  crucibles,  192. 

Antimony,  effect  of,  24. 

Arsenic,  effect  of,  24. 

Arseniureted  hydrogen  in  precipitate 
treatment,  181,  211. 

Assay  of  base  metals  in  cyanide  solu- 
tion, 53. 

of  gold  and  silver  in  cyanide  solu- 
tion, 50. 
of  zinc  precipitate,  195. 

Atomic  weights,  273. 

Available    cyanide,    definition    and 
test,  48. 


B. 

Barium  cyanide,  9. 

Base    metals    in    cyanide    solutions, 

assay  of,  53. 
Basic  slag,  185,  190. 
Bibliography,  classified,  213. 
Bisulphate  of  sodium  treatment  of 

precipitate,  182,  183. 
Borates  in  precipitate  melting,  185, 

187,  189. 
Borax  and  borax  glass  as  fluxes,  185, 

187,  189,  190. 

Bottle  tests  in  ore-testing,  69,  71,  72.. 
Bromocyanide,  Use  of,  12,  204,  206. 
Brown  air-agitator,  116,  121. 
Burt  rapid  filter,  152. 
revolving  filter,  152. 
Butters  and  Mein  sand  distributor, 

3,92. 
filter,  140. 


283 


284 


INDEX 


C. 

Calcium.     (See  Lime.) 

cyanide,  9. 
Capacity  of  tanks,  formulae  and  table, 

274,  275. 
Carbon    and    carbonaceous    matter, 

effect  of,  26,  64. 
Carbonic   acid   neutralized   by   lime 

and  alkalinity,  59. 
acid  of  air  in  agitation,  124. 
Caustic  alkalis.     (See  Lime.) 

soda   and   potash,    standard   solu- 
tions, 39,  41. 
Causticity  of  lime,  determination  of, 

63. 
Center-washing  in  Merrill  filter  press, 

137,  155. 
Centrifugal  pumps  in  agitation,  119, 

120,  121. 

Chemistry  of  cyanide  solutions,  chap- 
ter on,  28. 
Chiddy-method  .assay     of     cyanide 

solutions,  51. 
Clarifying    cyanide    solutions,    127, 

161,  162. 

Classification  of  leaf  filters,  140,  154. 
of  ores  in  cyaniding,  21. 
of  sand  and  slime,  91,  111. 
Classified  bibliography,  213. 
Clay  liners  in  graphite  crucibles,  191. 
Cleaning-up,  chapter  on,  176. 
Cobalt,  effect  of,  26. 

solution  for  cyanide  poisoning,  209. 
Concentrate  cyaniding,,  aeration,  199. 
cyaniding,  agitation  and  fine  grind- 
ing, 201. 

cyaniding,  chapter  on,  197. 
cyaniding,  filtration,  201. 
cyaniding,  general  considerations, 

202. 
cyaniding,  lime  and  alkalinity  in, 

198,  200. 

cyaniding,  percolation,  197. 
cyaniding,  preliminary  acid  treat- 
ment, 204. 

testing  by  cyanide,  78. 
Continuous  agitation,  115. 
decantation,  129. 


Copper,  effect  of,  23. 

in  solution,  170. 

Crucibles.     (See  Graphite  crucibles.) 
Crushing,  effect  of  size  of,  16. 

testing  for  fineness  required,  72. 
Cyanates,  49. 
Cyanic  acid,  49. 
Cyanicides,  14. 
Cyanide,  action  on  sulphides,  19,  45. 

addition  in  agitation,  113. 

consumption,  increased  by  agita- 
tion, 124. 

consumption,  test  for  cause  of,  83. 

decomposition  of,  10,  49. 

definition  of,  7. 

difference  between  potassium,  sodi- 
um, and  other  cyanides,  9. 

discovery  and  early  use,  1. 

double,  action  of,  36. 

how  added  to  solution,  100. 

manufacture  of,  9. 

mechanically   lost   in  percolation, 
106. 

poisoning,  chapter  on,  207. 

poisoning  in   precipitate   refining, 
210. 

poisoning,  prevention,  211. 

poisoning,   treatment  with  cobalt 
solution,  209. 

poisoning,  treatment  with  ferrous 
salts,  209. 

poisoning,  treatment  with  hydro- 
gen peroxide,  208. 

process,  development,  3. 

process,  discovery,  2. 

properties  and  reactions,  7. 

regeneration  by  lime,  36. 

regeneration  by  mercury,  or  mer- 
cury salts,  12,  44. 

regeneration  in  zinc  box,  173. 

simple  and  double,  8. 

solubility  of  potassium,  9. 

solution,  action  of  weak  and  strong, 
in  precipitation,  58,  160. 

solution,  assay  of  base  metal  in,  53. 

solution,  assay  of  gold  and  silver 
in,  50. 

solution,  chemistry  of,  28. 


INDEX 


285 


Cyanide,    solution,    clarifying,    127, 
161,  162. 

solution,  determining  strength  to 
be  used,  69. 

solution,  handling  and  control  of, 
during  percolation,  96-107. 

solution,  heating,  15. 

solution,  how  standardized,  99. 

solution,  nature  of  acid,  34. 

solution,    quantity   necessary,    17, 
114. 

solution,  selective  action,  14. 

solution,  strength  required,  13. 

solution,  test  for  acidity,  33. 

solution,    test    for    alkaline    sul- 
phides, 48. 

solution,    test   for   available   cya- 
nide, 48. 

solution,  test  for  double  cyanides, 
35. 

solution,  test  for  ferri-  and  ferro- 
cyanides,  44. 

solution,  test  for  free  cyanide,  29. 

solution,  test  for  hydrocyanic  acid, 
32. 

solution,  test  for  protective  alka- 
linity, 38. 

solution,  test  for  reducing  power, 
49. 

solution,  test  for  total  alkalinity, 
43. 

solution,  test  for  total  cyanide,  35. 

solution,  zinc  in,  172. 

testing  solid,  32. 

various  simple  cyanides,  9. 
Cyanogen,  definition  of,  7. 

greater  affinity  for  certain  metals,  8. 

source  of,  8. 

D. 
Decantation  by  mechanical  means, 

129. 

chapter  on,  125. 
continuous,  129. 
imperfections  of,  126. 
preceding  filtration,  125,  130. 
in  practice,  126,  127. 
theory  of,  125. 


Decomposition  of  cyanide,  10,  49. 
Dehne    plate-and-frame    filter   press 

in  Australia,  133. 
Depth  of  sand  vats,  93,  199. 
Development  of  cyanide  process,  3. 
Direct-filling  of  sand  vats,  90. 
Discovery  of  cyanide  process,  2. 
Dissolution  of  gold  and  silver,  chap- 
ter on,  11. 

time  required,  18. 
Distributor  for  sand  vats,  90,  91. 
Dorr  classifier,  91,  111. 

pulp-thickener,  112,  129. 
Double  cyanides,  action  of,  36. 

cyanides,  definition  of,  8. 

cyanides,  test  for,  35. 
Dressing  zinc  boxes,  165,  167. 
Dry-crushed  ore,  percolation  of,  89. 
Drying  ore,  205. 

E. 

Electrical  precipitation,  5,  159. 
Electrolytes  in  slime  settlement,  110. 
Extraction,  test  for  cause  of  poor,  82. 
tests.     (See  Ore-testing.) 

F. 

Ferri-  and  ferrocyanides,  decomposi- 
tion by  mercury  salts,  12,  44. 

and  ferrocyanides,  occurrence,  ac- 
tion and  test,  43,  44. 
Ferrous  salts  in  cyanide  poisoning, 

209. 

Filter,  leaf,  building-up  of  solution, 
157. 

leaf,  Burt  rapid,  152. 

leaf,  Burt  revolving,  152. 

leaf,  Butters,  140. 

leaf,  classification  of,  140,  154. 

leaf,  comparison  of  types,  156. 

leaf,  encrustation  by  lime,  59, 158. 

leaf,   general   considerations,    137, 
154. 

leaf,   granular  material  for  cake, 
137,  155. 

leaf,  Hunt,  146,  157. 

leaf,  Kelly,  148,  201. 

leaf,  Moore,  140. 


286 


INDEX 


Filter,  leaf,  Oliver,  143,  157. 
leaf,  Ridgeway,  148,  156. 
press,  plate-and-frame,  centerwash- 

ing  in  Merrill  type,  137. 
press,      plate-and-frame,      Dehne 

type  in  Australia,  133. 
press,     plate-and-frame,     descrip- 
tion, 131. 

press,    plate-and-frame,    in    prac- 
tice, 133. 
press,      plate-and-frame,      Merrill 

type,  135,  155. 
press,     plate-and-frame,     use     of 

monteju,  133. 
Filtration,  chapter  on,  131. 

of  concentrate,  201. 
Fine-grinding,  16,  202. 
Fluor  spar  as  a  flux,  186,  190. 
Fluxes  in  melting,  borax  and  borax 

glass,  185,  187,  189,  190. 
in    melting,     manganese    dioxide, 

186,  189,  191. 

in  melting,  niter,  186, 189, 191, 195. 
in  melting,  silica,  186,  187,  189, 190. 
in  melting,  sodium  and  potassium 
carbonates,  185,  187,  189,  190, 
191. 
Fluxing,  185,  187,  190. 

and  melting,  chapter  on,  184. 
preparation  of  precipitate  and  flux, 

192. 

variations  due  to  zinc,  188. 
Foul  solutions,  15. 
Free  acidity  in  ore,  test  for,  68. 
acidity,    removal    in    plant    prac- 
tice, 97. 

cyanide,  definition  and  test,  29. 
Furnace,  melting,  192. 

G. 

Gold  and  silver,  dissolution  by  cy- 
anide, 11. 
and    silver    mechanically    lost    in 

percolation,  106. 
Graphite    crucibles,    action    of    oxi- 

dizers  on,  186,  189. 
crucibles,  annealing,  192. 
crucibles,  clay-liners,  191. 


Graphite  crucibles,  composition,  189. 
crucibles,  treatment  after  use,  194. 
effect  in  cyaniding,  26. 

H. 

Heating  cyanide  solution,  15. 

Hendryx  agitator,  121. 

History  and  development  of  cyanide 

process,  chapter  on,  1. 
Hunt  filter,  146,  157. 
Hydrocyanic    acid,    occurrence,    26, 
32,  56,  59,  124,  181,  207,210,211. 
poisonous  effects,  207,  210,  211. 
acid,  test  for,  32. 
acid  treatment  of  precipitate,  180, 

182. 
Hydrogen   in   precipitation,    26,    59, 

167. 
peroxide  in  cyanide  poisoning,  208. 

I. 

Indicator,  potassium  iodide,  29,  31. 

Indicators     of     acidity     and     alka- 
linity, 39. 

Interfering  substances,  21. 

Iron,  effect  of,  23,  43,  56. 

oxidation    and    neutralization    by 
alkali,  56,  200. 

J. 

Just  silica-sponge  brick  agitator,  117, 
123. 

K. 
Kelly  filter,  148,  201. 

L. 

Latent  acidity  of  ore,  test  for,  68. 
acidity,  removal  in  plant  practice, 

97. 

Law  of  mass  action,  46. 
Leaching.     (See  Percolation.) 
Leaching  rate,  definition  and  test,  80. 
Lead  acetate,  use  in  ore-testing,  70, 

78. 

acetate,  use  in  precipitating  alka- 
line sulphides,  46,  47. 
acetate,    use   in   zinc-lead   couple, 


INDEX 


287 


Lead,  effect  of,  24. 

in  precipitate,  fluxing  of,  189. 

smelting  of  zinc  precipitate,  195. 

tray  assay  of  cyanide  solution,  50. 
Leaf  filter.     (See  Filter,  leaf.) 
Lime,  action  on  sulphide,  37,  45,  60, 
200. 

action  on  zinc  and  use  in  precipita- 
tion, 58,  160,  167,  169. 

amount  required  in  practice,  60,  63. 

and  alkalinity,  chapter  on,  54. 

and  caustic  soda  compared,  63. 

as  a  flux,  190. 

as  neutralizer  of  carbonic  acid,  59. 

as  neutralizer  of  iron  and  other 
salts,  55. 

determining  amount  required,  68, 
69,  82. 

determining  causticity  of,  63. 

dissolving  effect  on  metals,  60. 

in  slime  settlement,  110,  112. 

method  of  application,  61,  98,  102, 
113,  198. 

on  filter  leaves,  59,  158. 

precipitation   of   gold   by   carbon 
of,  64. 

properties,  varieties,  and  uses,  54. 

reducing  agents  in,  64. 

regeneration  of  cyanide  by,  36. 

solubility  of,  54,  274. 

water,  54. 

Litharge,  use  in  precipitating  alka- 
line sulphides,  47. 

M. 

MacArthur-Forrest  process,  2. 
Magnesium  cyanide,  9. 

effect  of,  26. 

Manganese  dioxide  as  a  flux,   186, 
189,  191. 

dioxide  as  an  oxidizer  in  ore  treat- 
ment, 12. 

effect  of,  in  ore,  26. 
Manufacture  of  cyanide,  9. 
Matte  from  precipitate  melting,  191. 

treatment  of  old,  194. 
Mechanical  agitators,  118,  128,  201. 

decantation  processes,  129. 


Melting  and  fluxing,  chapter  on,  184. 
furnace,  192. 

with  litharge  and  cupellation,  195. 
Mercury,  effect  of,  in  ore,  25. 

and  mercury  salts,  use  of,  in  de- 
composing ferrocyanides,  12,  44. 
and  mercury  salts,  use  of,  in  pre- 
cipitating alkaline  sulphides,  13, 
25,  47,  171. 

in  precipitation,  25,  171. 
Merrill  filter  press,  135,  155. 
Methyl   orange    indicator,    prepara- 
tion, 39. 

Milk-of-lime,  54. 

Moisture  retained  in  percolation,  105. 
Moore  filter,  140. 
Monteju  with  filter  press,  133. 

N. 

Nickel,  effect  of,  26. 
Niter,  use  in  melting,  186,  189,  191, 

195. 

use  in  roasting,  180,  182. 
Nitric  acid  treatment  of  precipitate, 
180,  181. 

O. 

Oliver  filter,  143,  157. 
Ore     testing,     agitation     extraction 
tests,  71. 

testing,  amalgamation  tests,  77. 

testing    and    physical    determina- 
tions, chapter  on,  65. 

testing,  bottle  tests,  69,  71,  72. 

testing  by  percolation,  71. 

testing,  cause  of  cyanide  consump- 
tion, 83. 

testing,  cause  of  low  extraction,  82. 

testing,     determining     cyanide 
strength  required,  69. 

testing,      determining     lime     re- 
quired, 68,  69. 

testing  during  plant  operation,  83. 

testing  for  fineness  of  crushing,  72. 

testing  for  leaching  rate,  81. 

testing  for  slime  settling  rate,  82. 

testing,  free  acidity  test,  68. 

testing,  latent  acidity  test,  68. 


288 


INDEX 


Ore  testing,  methods  of,  65,  79. 
testing  of  concentrate,  78. 
testing  on  large  scale,  80. 
testing,    physical    examination   of 

ore,  67. 

testing,  precipitation  tests,  83. 
testing,  samples  for,  66. 
testing,  sizing  tests,  73. 
testing,     specific     gravity     deter- 
minations, 84. 

testing,  total  acidity  test,  68. 
Oxidation  of  iron  salts,  57,  103,  200. 
Oxidizers   in   melting  and   roasting, 

180,  182,  186,  189,  191,  195. 
in  ore  treatment,  12,  43. 
Oxidizing  roast  of  ore,  205. 
Oxygen  in  cyanide  process,  11,  13,  15, 
17,  23,  45,  57,    102,    103,    114, 
199,  200. 

P. 

Pachuca  tanks,  116,  121. 
Percolation,  aeration,  102. 

application  of  lime,  97. 

application  of  solution,  96. 

arrangement  of  leaching  plant,  93. 

chapter  on,  87. 

classification  for,  91,  111. 

continuous    or    alternative    wash- 
ing, 103. 

cyanide  and  dissolved  metal  dis- 
charged, 106. 

depth  of  charge,  81,  93,  199. 

determining    progress  of    dissolu- 
tion, 102. 

direct-filling,  90. 

fineness  of  ore,  93. 

handling  and  control  of  solutions, 
96-107. 

leaching  rate,  80. 

moisture  retained  by  sand,  105. 

of  dry-crushed  ore,  89. 

strength  of  solution,  14. 

tailing  deposit  treatment,  87. 

tests  in  laboratory,  71. 

transfer  after  direct-filling,  92. 

variation  of  space  due  to  settle- 
ment or  transfer,  92,  96,  272. 


Percolation,  water-washing   and  re- 
moval of  cyanicides,  97. 
Phenolthalein     indicator,      prepara- 
tion, 39. 
Physical     determinations     and     ore 

testing,  chapter  on,  65. 
Plate-and-frame    filter    press.     (See 

Filter  press.) 

Plant  arrangement  in  percolation,  93. 
Poisoning,    cyanide.      (See    Cyanide 

poisoning.) 

Potassium  carbonates  as  fluxes,  185, 
187,  189,  190,  191. 

cyanide.     (See  Cyanide.) 

iodide  in  free  cyanide  test,  29,  31. 

nitrate   in   roasting   and   melting, 
180,  182,  186,  189,  191,  195. 

permanganate    as   an   oxidizer   in 

ore  treatment,  12. 
Precipitate,  assay  of,  195. 

constituents  for  melting,  184. 

fluxing  and  melting,   chapter  on, 
184. 

melting  with  litharge  and  cupella- 
tion,  195. 

refining,     arseniureted    hydrogen, 
181. 

refining  by  acid,  180. 

refining  by  bisulphate  of  sodium, 
182,  183. 

refining  by  hydrochloric  acid,  180, 
182. 

refining  by  nitric  acid,  180. 

refining  by  sulphuric  acid,  181. 

refining  by  sulphurous  acid,  183. 

refining,  cyanide  poisoning  in,  210. 

refining,    hot   and   cold   washings, 
182. 

roasting,  179,  182. 

Precipitation  by   carbon  in   ore  or 
lime,  26,  64. 

care  of,  165,  167. 

chapter  on,  159. 

clarifying  solutions,  127,  161,  162. 

cleaning-up,  176. 

copper  in  solution,  23,  170. 

electrical,  5,  159. 

hydrogen  in  zinc  boxes,  26,  59,  167. 


INDEX 


289 


Precipitation,  lime  and  alkalinity  in, 

58,  160,  167,  169. 

mechanical     and     chemical     con- 
sumption of  zinc,  171. 
mercury  in,  25,  171. 
poor,  168. 
reactions  in,  159. 
regeneration  of  cyanide  and  alkali, 

173. 

tests  in  ore  testing,  83. 
weak    and     strong     solution    in, 

160. 

white  precipitate,  58,  160,  168. 
zinc  box,  161. 
zinc   box,    packing   and   dressing, 

165,  167. 
zinc  dust,  173. 
zinc-lead  couple,  170. 
zinc    shavings,    amount    required 

and  consumption,  163,  172. 
zinc  shavings,  cutting,  171. 
zinc  shavings,  size  required,  163. 
Pressure    leaf    filters.     (See    Filter, 

leaf.) 
Protective  alkalinity,  definition  and 

test  for,  38. 

alkalinity,  uses  of.     (See  Lime.) 
Prussian  blue,  57. 
Pulp  thickening,  112,  113. 

R. 

Rate  of  leaching,  80. 
Reducing  power  of  cyanide  solution, 

test  for,  49. 

Refining   precipitate.     (See   Precipi- 
tate refining.) 

Refractory  ores,  nature  of,  21. 
Regeneration  of  cyanide  and  alkali 

in  zinc  box,  173. 
of  cyanide  by  alkali,  36. 
of  cyanide  by  mercury  and  mer- 
cury salts,  12,  44. 
Ridgeway  filter,  148,  156. 
Roasting  and  acid  treatment  of  pre- 
cipitate, chapter  on,  179. 
ore,  chapter  on,  205. 
ore,  test  in,  206. 
use  of  niter,  180,  182. 


S. 

Samples  for  ore  testing,  66. 
Sand  and  rock,  table  of  weight,  272. 

and  slime  separation,  91,  111. 

filters  for  clarifying,  127,  161. 

treatment.     (See  Percolation.) 
Selective  action  of  cyanide,  14. 
Settlement    of    slime.     (See    Slime 

settlement.) 

Shavings,  zinc.     (See  Zinc  shavings.) 
Short  zinc,  cause  of,  171. 

zinc,  disposal  in  clean-up,  177. 
Silica  as  a  flux,  186,  187,  189,  190. 
Silicates  in  precipitate  melting,  185, 

186,  187,  189. 
Siliceous  slag,  185,  190. 

Silver,    dissolution   by   cyanide,    11, 
19. 

nitrate  test  for  free  cyanide,  29. 

nitrate   test   for   total   or   double 
cyanides,  35. 

ores  amenable  to  treatment,  27. 

treatment  for,  19. 
Simple  cyanides,  definition,  8. 
Size  of  metal  particles,  effect  of,  16. 
Sizing  tests,  73. 
Slag,  basic  and  siliceous,  185,  190. 

pouring  and  latter  treatment,  194. 
Slime  agitation.     (See  Agitation.) 

definition  and  characteristics,  108. 

in  tailing  deposits,  88. 

pulp,    specific    gravity    table    of, 
276-281. 

separation,  91,  111. 

settlement,  109. 

settlement,  influence  of  depth,  110. 

settlement,  lime  in,  109. 

settling  rate,  test  for,  82. 

thickening,  112,  113. 

treatment  and  agitation,  chapter 

on,  108. 
Sluicing-bar  of   Merrill  filter  press, 

136. 

Smelting.     (See  melting.) 
Sodium    carbonates   as   fluxes,    185, 

187,  189,  190,  191. 
cyanide.     (See  Cyanide.) 
peroxide  as  oxidizer,  12. 


290 


INDEX 


Solubilities    of    various    chemicals, 
table,  274. 

Solubility  of  lime,  54,  274. 
of  potassium  cyanide,  9. 

Soluble  sulphides.     (See  Alkaline  sul- 
phides and  sulphocyanides.) 

Solution,  cyanide.     (See  Cyanide  so- 
lution.) 

Solutions,  standard  acid  and  alkali, 

preparation,  39. 
standard  acid  and  alkali,  tables  of 

equivalents,  42. 
standard  acid  and  alkali,  theory, 

39. 

standard  caustic  soda  and  potash, 
39,  41. 

Specific  gravity  determinations,  84. 
gravity  of  slime  pulp,  table,  276- 
281. 

Standard     solutions.         (See    Solu- 
tions.) 

Strength    of    cyanide    solution    re- 
quired, 13,  115. 

Strong    solution    in    plant    practice, 
94-105. 

Strontium  cyanide,  9. 

Sulphides.     (See  Concentrate.) 

Sulphocyanides.     (See  Alkaline  sul- 
phides and  sulphocyanides.) 

Sulphur,  effect  of,  in  melting,   189, 

191,  195. 
effect  of,  in  ore,  23. 

Sulphuric  acid  treatment  of  precipi- 
tate, 181. 

Sulphurous   acid  treatment   of  pre- 
cipitate, 183. 


T. 

Tables,  chapter  of,  269. 
Tailing  deposits,  treatment  by  per- 
colation, 87. 
settlement  in  ponds,  88. 
Tanks,  classification  of,  87,  94. 
volume  of,  formulae  and  table,  274, 

275. 

Tellurium,  effect  of,  25. 
Test  for  complete  roast,  206. 


Test  for  cyanide  and  dissolved  gold 
mechanically  lost  in  percolation, 
107. 

Testing  for  precipitate  flux,  186. 
ore.     (See  Ore  testing.) 
solid  cyanide,  32. 

solution.     (See  Cyanide  solution.) 
Thickening  of  pulp,  112,  113. 
Thiocyanates.     (See     Alkaline     sul- 
phides and  sulphocyanides.) 
Time  required  for  dissolution,  18. 

required  in  agitation,  115. 
Total  acidity  in  ore,  test  for,  68. 
acidity  in  plant  practice,  97. 
alkalinity,  definition  and  test  for, 

43. 

cyanide,  definition  and  test  for,  35. 
cyanogen,  49. 
Treatment     of     concentrate.     (See 

Concentrate  cyaniding.) 
of  matte,  194. 

of  slag  and  old  crucibles,  194. 
Trent  agitator,  121. 

V. 

Vacuum     leaf     filter.     (See     Filter, 

leaf.) 
Volume  of  tanks,  table  and  formulae, 

274,  275. 

W. 

Water,  table  of  weight  and  measure, 

272. 
washing  in  percolation,  97,  105, 

106. 
Weak  solution  in  plant  practice,  94, 

105. 
White  precipitate  of  zinc  boxes,  58, 

160,  168. 

Z. 

Zincates,  how  formed  in  precipita- 
tion, 160. 
Zinc  box,  161. 

box,    packing   and   dressing,    165, 

167. 

dust  precipitation,  173. 
effect  of,  in  ore,  25. 


INDEX  291 

Zinc  in  precipitate,  fluxing,  188.  Zinc  precipitate,  assay  of,  195. 

in  solution,  accumulation,  171.  precipitation.     (See  Precipitation.) 

in  solution,  action  on  alkaline  sul-  shavings,    amount    required    and 

phides,  46.  consumption,  163,  172. 

lead  couple,  170.  shavings,  cutting,  171. 

potassium  cyanide  as  a  solvent,  36.  shavings,  size  required,  163. 


RETURN  TO  the  circulation  desk  of  any 
University  of  California  Library 
or  to  the 

NORTHERN  REGIONAL  LIBRARY  FACILITY 
Bldg.  400,  Richmond  Field  Station 
University  of  California 
Richmond,  CA  94804-4698 

ALL  BOOKS  MAY  BE  RECALLED  AFTER  7  DAYS 
2-month  loans  may  be  renewed  by  calling 

(510)642-6753 
1-year  loans  may  be  recharged  by  bringing  books 

to  NRLF 
Renewals  and  recharges  may  be  made  4  days 

prior  to  due  date 


DUE  AS  STAMPED  BELOW 


HOY  3  0  1992 


YC   18752 


THE  UNIVERSITY  OF  CALIFORNIA  LIBRARY 


